Fiber delivered laser induced white light system

ABSTRACT

The present disclosure provides an apparatus for generating fiber delivered laser-induced white light. The apparatus includes a package case enclosing a board member with an electrical connector through a cover member and a laser module configured to the board member inside the package case. The laser module comprises a support member, at least one laser diode device configured to emit a laser light of a first wavelength, a set of optics to guide the laser light towards an output port. Additionally, the apparatus includes a fiber assembly configured to receive the laser light from the output port for further delivering to a light head member disposed in a remote destination. A phosphor material disposed in the light head member receives the laser light exited from the fiber assembly to induce a phosphor emission of a second wavelength for producing a white light emission substantially reflected therefrom for various applications.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. application Ser. No.17/563,986, filed Dec. 28, 2021 which is a continuation of U.S.application Ser. No. 16/230,158, filed Dec. 21, 2018, the entirecontents of which are incorporated herein by reference in its entiretyfor all purposes.

BACKGROUND

In the late 1800's, Thomas Edison invented the light bulb. Theconventional light bulb, commonly called the “Edison bulb,” has beenused for over one hundred years for a variety of applications includinglighting and displays. The conventional light bulb uses a tungstenfilament enclosed in a glass bulb sealed in a base, which is screwedinto a socket. The socket is coupled to an AC power or DC power source.The conventional light bulb can be found commonly in houses, buildings,and outdoor lightings, and other areas requiring light or displays.Unfortunately, drawbacks exist with the conventional light bulb:

-   -   The conventional light bulb dissipates more than 90% of the        energy used as thermal energy.    -   The conventional light bulb routinely fails due to thermal        expansion and contraction of the filament element.    -   The conventional light bulb emits light over a broad spectrum,        much of which is not perceived by the human eye.    -   The conventional light bulb emits in all directions, which is        undesirable for applications requiring strong directionality or        focus, e.g. projection displays, optical data storage, etc.

To overcome some of the drawbacks of the conventional light bulb,several alternatives have been developed including fluorescent lamps,Mercury vapor lamps, sodium vapor lamps, other high-intensity discharge(HID) lamps, gas discharge lamps such as neon lamps, among others. Theselamp technologies in general suffer from similar problems to Edisonlamps as well as having their own unique drawbacks. For example,fluorescent lamps require high voltages to start, which can be in therange of a thousand volts for large lamps, and also emit highlynon-ideal spectra that are dominated by spectral lines.

In the past decade, solid state lighting has risen in importance due toseveral key advantages it has over conventional lighting technology.Solid state lighting is lighting derived from semiconductor devices suchas diodes which are designed and optimized to emit photons. Due to thehigh efficiency, long lifetimes, low cost, and non-toxicity offered bysolid state lighting technology, light emitting diodes (LED) haverapidly emerged as the illumination technology of choice. An LED is atwo-lead semiconductor light source typically based on a p-i-n junctiondiode, which emits electromagnetic radiation when activated. Theemission from an LED is spontaneous and is typically in a Lambertianpattern. When a suitable voltage is applied to the leads, electrons andholes recombine within the device releasing energy in the form ofphotons. This effect is called electroluminescence, and the color of thelight is determined by the energy band gap of the semiconductor.

Appearing as practical electronic components in 1962 the earliest LEDsemitted low-intensity infrared light. Infrared LEDs are still frequentlyused as transmitting elements in remote-control circuits, such as thosein remote controls for a wide variety of consumer electronics. The firstvisible-light LEDs were also of low intensity, and limited to red.Modern LEDs are available across the visible, ultraviolet, and infraredwavelengths, with very high brightness.

The earliest blue and violet gallium nitride (GaN)-based LEDs werefabricated using a metal-insulator-semiconductor structure due to a lackof p-type GaN. The first p-n junction GaN LED was demonstrated by Amanoet al. using the LEEBI treatment to obtain p-type GaN in 1989. Theyobtained the current-voltage (I-V) curve and electroluminescence of theLEDs, but did not record the output power or the efficiency of the LEDs.Nakamura et al. demonstrated the p-n junction GaN LED using thelow-temperature GaN buffer and the LEEBI treatment in 1991 with anoutput power of 42 μW at 20 mA. The first p-GaN/n-InGaN/n-GaN DH blueLEDs were demonstrated by Nakamura et al. in 1993. The LED showed astrong band-edge emission of InGaN in a blue wavelength regime with anemission wavelength of 440 nm under a forward biased condition. Theoutput power and the EQE were 125 μW and 0.22%, respectively, at aforward current of 20 mA. In 1994, Nakamura et al. demonstratedcommercially available blue LEDs with an output power of 1.5 mW, an EQEof 2.7%, and the emission wavelength of 450 nm. On Oct. 7, 2014, theNobel Prize in Physics was awarded to Isamu Akasaki, Hiroshi Amano andShuji Nakamura for “the invention of efficient blue light-emittingdiodes which has enabled bright and energy-saving white light sources”or, less formally, LED lamps.

By combining GaN-based LEDs with wavelength converting materials such asphosphors, solid-state white light sources were realized. Thistechnology utilizing GaN-based LEDs and phosphor materials to producewhite light is now illuminating the world around us as a result of themany advantages over incandescent light sources including lower energyconsumption, longer lifetime, improved physical robustness, smallersize, and faster switching. LEDs are now used in applications as diverseas aviation lighting, automotive headlamps, advertising, generallighting, traffic signals, and camera flashes. LEDs have allowed newtext, video displays, and sensors to be developed, while their highswitching rates can be very useful in communications technology. LEDs,however, are not the only solid-state light source and may not bepreferable light sources for certain lighting applications. Alternativesolid state light sources utilizing stimulated emission, such as laserdiodes (LDs) or super-luminescent light emitting diodes (SLEDs), providemany unique features advantageously over LEDs.

In 1960, the laser was demonstrated by Theodore H. Maiman at HughesResearch Laboratories in Malibu. This laser utilized a solid-state flashlamp-pumped synthetic ruby crystal to produce red laser light at 694 nm.Early visible laser technology comprised lamp pumped infrared solidstate lasers with the output wavelength converted to the visible usingspecialty crystals with nonlinear optical properties. For example, agreen lamp pumped solid state laser had 3 stages: electricity powerslamp, lamp excites gain crystal which lases at 1064 nm, 1064 nm goesinto frequency conversion crystal which converts to visible 532 nm. Theresulting green and blue lasers were called “lamped pumped solid statelasers with second harmonic generation” (LPSS with SHG) had wall plugefficiency of ˜1%, and were more efficient than Ar-ion gas lasers, butwere still too inefficient, large, expensive, fragile for broaddeployment outside of specialty scientific and medical applications. Toimprove the efficiency of these visible lasers, high power diode (orsemiconductor) lasers were utilized. These “diode pumped solid statelasers with SHG” (DPSS with SHG) had 3 stages: electricity powers 808 nmdiode laser, 808 nm excites gain crystal, which lases at 1064 nm, 1064nm goes into frequency conversion crystal which converts to visible 532nm. As high power laser diodes evolved and new specialty SHG crystalswere developed, it became possible to directly convert the output of theinfrared diode laser to produce blue and green laser light output. These“directly doubled diode lasers” or SHG diode lasers had 2 stages:electricity powers 1064 nm semiconductor laser, 1064 nm goes intofrequency conversion crystal which converts to visible 532 nm greenlight. These lasers designs are meant to improve the efficiency, costand size compared to DPSS-SHG lasers, but the specialty diodes andcrystals required make this challenging today.

Solid-state laser light sources, due to the narrowness of their spectrawhich enables efficient spectral filtering, high modulation rates, andshort carrier lifetimes, smaller in size, and far greater surfacebrightness compared to LEDs, can be more preferable as visible lightsources as a means of transmitting information with high bandwidth inmany applications including lighting fixtures, lighting systems,displays, projectors and the like. Advancements of new GaN-based bluelaser technology based on improved processes have substantially reducedmanufacture cost and opened opportunities for utilizing the modulatedlaser signal and the light spot directly to measure and or interact withthe surrounding environment, transmit data to other electronic systems,and respond dynamically to inputs from various sensors. Suchapplications are herein referred to as “smart lighting” applications tobe disclosed throughout the specification herein.

SUMMARY

The present invention provides a fiber-delivered phosphor-emitted whitelight system and method of making the same. Merely by examples, theinvention provides laser pumped phosphor light sources from gallium andnitrogen containing laser diodes, white light source integrated with afiber attached phosphor in packaging and laser pump-light deliveryconfiguration. The invention is applicable to many applicationsincluding static lighting devices and methods, dynamic lighting devicesand methods, LIDAR, LiFi, and visible light communication devices andmethods, and various combinations of above in applications of generallighting, commercial lighting and display, automotive lighting andcommunication, defense and security, industrial processing, and internetcommunications, and others.

Specific embodiments of this invention employ a transferred gallium andnitrogen containing material process for fabricating laser diodes orother gallium and nitrogen containing devices (as shown in U.S. Pat.Nos. 9,666,677 and 9,379,525, filed by one of inventors of thisapplication) enabling benefits over conventional fabricationtechnologies.

In some embodiments, beam shaping elements such as MEMS scanningmirrors, and communications triggered by integrated sensor feedback areemployed to generate smart laser lighting. The smart laser lighting canbe combined with LIDAR technology for enhanced system functionalityand/or enhanced LIDAR function. Specific embodiments of this inventionemploy a transferred gallium and nitrogen containing material process(U.S. Pat. Nos. 9,666,677 and 9,379,525) for fabricating laser diodes orother gallium and nitrogen containing devices enabling benefits overconventional fabrication technologies.

Optionally, the phosphor material used in the fiber-delivered smartlaser lighting system is comprised of a ceramic yttrium aluminum garnet(YAG) doped with Ce or a single crystal YAG doped with Ce or a powderedYAG comprising a binder material. The phosphor has an optical conversionefficiency of greater than 50 lumen per optical watt, greater than 100lumen per optical watt, greater than 200 lumen per optical watt, orgreater than 300 lumen per optical watt.

Optionally, a waveguide element is used to transport the laserexcitation pump source to the remote wavelength converter element suchas a phosphor element. In a preferred embodiment, the transportwaveguide is an optical fiber wherein the optical fiber could becomprised of a single mode fiber (SMF) or a multi-mode fiber (MMF), withcore diameters ranging from about 1 um to 10 um, about 10 um to 50 um,about 50 um to 150 um, about 150 um to 500 um, about 500 um to 1 mm, orgreater than 1 mm. The optical core material may consist of a glass suchas silica glass wherein the silica glass could be doped with variousconstituents and have a predetermined level of hydroxyl groups (OH) foran optimized propagation loss characteristic. The glass fiber materialmay also be comprised of a fluoride glass, a phosphate glass, or achalcogenide glass. In an alternative embodiment, a plastic opticalfiber is used to transport the laser pump light.

Optionally, the phosphor material is configured to operate in a modeselected from a reflective mode, a transmissive mode, and a combinationof a reflective mode and a transmissive mode in association withreceiving the first laser beam with the first peak wavelength to excitethe emission with the second peak wavelength.

Optionally, the integrated package includes the wavelength conversionmember configured as a remote pumped phosphor and an optical fiber toguide the laser beam from the gallium and nitrogen containing laserdiode to the remote pumped phosphor.

Optionally, the at least one gallium and nitrogen containing laser diodeincludes multiple laser diodes such as 2 laser diodes, 3 laser diodes,or 4 laser diodes to generate 2 laser beams, 3 laser beams, or 4 laserbeams, respectively. The multiple laser beams form an excitation spot onthe wavelength conversion member.

Optionally, each of the multiple laser diodes is characterized by one ofmultiple first peak wavelengths in 420 nm to 485 nm blue color range.The multiple first peak wavelengths result in an improved color qualityof the white light.

Optionally, the wavelength conversion member includes a first phosphormaterial configured to be excited by the first laser beam with the firstpeak wavelength to produce a first emission of a second peak wavelengthand a second phosphor material configured to be excited by the laserbeam to produce a second emission with a third peak wavelength.

Optionally, the gallium and nitrogen containing laser diode ischaracterized by the first laser beam with the first peak wavelength inviolet color range. The first phosphor material is characterized by thefirst emission with the second peak wavelength in blue color range. Thesecond phosphor material is characterized by the second emission withthe third wavelength in yellow color range. The white light is comprisedof at least the first emission and the second emission.

Optionally, the beam projector includes a MEMS or other micro-controlledscanner or display module, micro-mirror, micro-lens, configured todynamically scan a beam of the sensing light signal across the remotetarget object.

Optionally, the blue laser light is characterized by high power levelsin one range selected from 1 mW to 10 mW, 10 mW to 100 mW, 100 mW to 1W, and 1 W to 10 W capable of sensing and mapping the remote targetobject under damp condition with relative humidity level in each offollowing ranges of greater than 25%, greater than 50%, greater than75%, and greater than 100%.

In a specific embodiment, the present invention provides an apparatusfor remotely delivering white light. The apparatus includes at least onelaser diode device. The apparatus further includes a package member withelectrical feedthroughs configured to couple power from a driver to theat least one laser diode device. The package member includes a supportmember. The at least one laser diode device is configured to the supportmember and driven by the driver to emit a beam of laser electromagneticradiation characterized by a first wavelength ranging from 395 nm to 490nm. Additionally, the apparatus includes a waveguide assembly having afirst end section coupled to the package member to receive the laserelectromagnetic radiation and a waveguide transport member to deliverthe laser electromagnetic radiation through a length to exit a secondend section with a propagation direction, a beam diameter, and adivergence. The apparatus further includes a phosphor member disposed ina light head member and configured with a surface to receive the laserelectromagnetic radiation exited from the second end section. Thephosphor member provides a wavelength conversion of at least a fractionof the laser electromagnetic radiation of the first wavelength to aphosphor emission of a second wavelength. The second wavelength islonger than the first wavelength. Furthermore, the apparatus includes amechanical fixture in the light head member configured to support thephosphor member and the second end section of the waveguide assemblywith an angle of incidence in a range from 5 degrees to 90 degreesbetween the primary propagation direction of the laser electromagneticradiation and a direction parallel the surface of the phosphor member.The laser electromagnetic radiation exiting the second end section ofthe waveguide assembly forms an excitation spot of the incident laserelectromagnetic radiation on the surface of the phosphor member. Theexcitation spot is characterized by a diameter ranging from 25 μm to 5mm. The excitation spot generates a substantially white light emissioncharacterized by a mixture of the laser electromagnetic radiation of thefirst wavelength and the phosphor emission of the second wavelength.

In another specific embodiment, the present invention provides anapparatus for remotely delivering white light. The apparatus includes apackage case enclosing an electronic board member with a multi-pinconnector. The apparatus further includes a laser module configured in asub-package plugged to the electronic board member inside the packagecase. The sub-package includes a support member, at least one galliumand nitrogen containing laser diode device configured to mount on thesupport member. The at least one gallium and nitrogen containing laserdiode device is configured to emit a beam of electromagnetic radiationcharacterized by a first wavelength ranging from 395 nm to 490 nm.Additionally, the apparatus includes a collimating lens configured inthe sub-package to collimate the beam of the electromagnetic radiationto an output port of the sub-package. The apparatus also includes a lidmember sealed the package case with the multi-pin connector coupled withan electrical feedthrough. Furthermore, the apparatus includes a fiberassembly comprising an optical fiber with a first end coupled to theoutput port to receive the electromagnetic radiation and deliver theelectromagnetic radiation through an arbitrary length to exit a secondend with a primary propagation direction, a beam diameter, and adivergence. The apparatus further includes a phosphor member disposedremotely in a light head member coupled with the second end of theoptical fiber. The phosphor member has a surface configured to receivethe electromagnetic radiation exiting the second end of the opticalfiber and provides a wavelength conversion of at least a fraction of theelectromagnetic radiation of the first wavelength to a phosphor emissionof a second wavelength, wherein the second wavelength is longer than thefirst wavelength. Moreover, the apparatus includes a mechanical fixturein the light head member configured to set a distance between thesurface of the phosphor member and the second end of the optical fiberand set an angle of incidence between the primary propagation directionof the electromagnetic radiation exiting the second end and a directionparallel the surface of the phosphor member to create an excitation spotof the electromagnetic radiation on the surface of the phosphor memberwith a diameter ranging from 25 μm to 5 mm. The excitation spotgenerates a white light emission characterized by a mixture of theelectromagnetic radiation of the first wavelength and the phosphoremission of the second wavelength.

In yet another specific embodiment, the present invention provides afiber-delivered laser-induced white light source for auto headlight. Thewhite light source includes a laser module packaged in a metal caseplugged to a circuit board, the metal case enclosing a support member,at least one laser diode device configured to mount on the supportmember and to emit a laser beam characterized by a wavelength rangingfrom 395 nm to 490 nm, and a collimating lens configured to guide thelaser beam to an output port. Additionally, the white light sourceincludes a focus lens coupled to the output port from outside the metalcase to receive and confine the laser beam. Furthermore, the white lightsource includes a fiber assembly embedding an optical fiber having afirst end section coupled to the output port with alignment to receivethe laser beam from the focus lens and deliver the laser beam throughthe optical fiber to a second end section. Moreover, the white lightsource includes a light head member disposed remotely in an autoheadlight module holding the second end section of the optical fibernear a phosphor material. The light head member is configured to directthe laser beam exiting the second end section of the optical fiber atthe phosphor material at an angle of incidence in a range from 5 degreesto 90 degrees between the laser beam and a direction parallel to asurface of the phosphor material to create a spot ranging from 50 μm to5 mm. The laser beam in the spot induces a phosphor-excited emissionwhich is partially mixed with the laser beam to produce a white lightemission as an illumination and projection light source of the autoheadlight module.

Merely by way of example, the present invention can be applied toapplications such as white lighting, white spot lighting, flash lights,automotive applications, automobile headlights or other lighting andcommunications functions, autonomous vehicles, all-terrain vehiclelighting, light sources used in recreational sports such as biking,surfing, running, racing, boating, light sources used for drones,planes, robots, other mobile or robotic applications, autonomous devicessuch as land, sea, or air vehicles and technology, safety, countermeasures in defense applications, multi-colored lighting, lighting forflat panels, medical, metrology, beam projectors and other displays,high intensity lamps, spectroscopy, entertainment, theater, music, andconcerts, analysis fraud detection and/or authenticating, tools, watertreatment, laser dazzlers, targeting, communications, LiFi, visiblelight communications (VLC), sensing, detecting, distance detecting,Light Detection And Ranging (LIDAR), transformations, transportations,leveling, curing and other chemical treatments, heating, cutting and/orablating, pumping other optical devices, other optoelectronic devicesand related applications, and source lighting and the like.

BRIEF DESCRIPTION OF THE FIGURES

The following drawings are merely examples for illustrative purposesaccording to various disclosed embodiments and are not intended to limitthe scope of the present invention.

FIG. 1 is a schematic diagram showing dependence of internal quantumefficiency in a laser diode on carrier concentration in the lightemitting layers of the device.

FIG. 2 is a plot of external quantum efficiency as a function of currentdensity for a high-power blue laser diode compared to the high powerblue light emitting diode.

FIG. 3 is a simplified schematic diagram of a laser diode formed on agallium and nitrogen containing substrate with the cavity aligned in adirection ended with cleaved or etched mirrors according to someembodiments of the present invention.

FIG. 4 is a cross-sectional view of a laser device according to anembodiment of the present invention.

FIG. 5 is a schematic diagram illustrating a chip on submount (CoS)based on a conventional laser diode formed on gallium and nitrogencontaining substrate technology according to an embodiment of thepresent invention.

FIG. 6 is a schematic representation of the die expansion process withselective area bonding according to some embodiments of the presentinvention.

FIG. 7 is a schematic diagram illustrating a CoS based on lifted off andtransferred epitaxial gallium and nitrogen containing layers accordingto an embodiment of this present invention.

FIG. 8A is a functional block diagram for a laser-based white lightsource containing a blue pump laser and a wavelength converting elementaccording to an embodiment of the present invention.

FIG. 8B is a functional block diagram for a laser-based white lightsource containing multiple blue pump lasers and a wavelength convertingelement according to another embodiment of the present invention.

FIG. 9A is a functional block diagram for a laser-based fiber-deliveredwhite light source according to an embodiment of the present invention.

FIG. 9B is a functional block diagram for a laser-based fiber-deliveredwhite light source according to another embodiment of the presentinvention.

FIG. 9C is a functional block diagram for a multi-laser-basedfiber-delivered white light source according to yet another embodimentof the present invention.

FIG. 10A is a simplified diagram illustrating a plurality of laser barsconfigured with optical combiners according to embodiments of thepresent invention.

FIG. 10B is a schematic diagram of an enclosed free space laser moduleaccording to a specific embodiment of the present invention.

FIG. 10C is a schematic diagram of an enclosed free space multi-chiplaser module with an extended delivery fiber plus phosphor converteraccording to another specific embodiment of the present invention.

FIG. 11 is a perspective view of a fiber-delivered white light sourceincluding a general laser package and a light head member linked eachother via a fiber assembly according to an embodiment of the presentinvention.

FIG. 12 is a top view of the general laser package of FIG. 11 accordingto the embodiment of the present invention.

FIG. 13 is a top view of interior elements of the general laser packageof FIG. 12 including a blue-laser module mounted on a circuit boardaccording to the embodiment of the present invention.

FIG. 14 is a top view of the blue-laser module with opened lid accordingto an embodiment of the present invention.

FIG. 15 is a perspective view of the blue-laser module according to theembodiment of the present invention.

FIG. 16 is (A) a top view of a general laser package, (B) a top view ofinterior elements of the general laser package including a blue-lasermodule, and (C) a top view of the blue-laser module according to anotherembodiment of the present invention.

FIG. 17 is a partial cross-sectional view of an end section of a fiberassembly according to an embodiment of the present invention.

FIG. 18 is a partial cross-sectional view of an end section of a fiberassembly according to another embodiment of the present invention.

FIG. 19 is a perspective view of the light head member of FIG. 11according to an embodiment of the present invention.

FIG. 20 shows an exemplary diagram of a fiber coupling joint made bymechanical butt coupler according to an embodiment of the presentinvention

FIG. 21 is a schematic diagram of a fiber-delivered white light sourcefor street pole light application according to an embodiment of thepresent invention.

DETAILED DESCRIPTION

The present invention provides a fiber-delivered phosphor-emitted whitelight system and method of making the same. Merely by examples, theinvention provides laser pumped phosphor light sources from gallium andnitrogen containing laser diodes, white light source integrated with afiber attached phosphor in packaging and pump-light deliveringconfiguration. The invention is applicable to many applicationsincluding dynamic lighting devices and methods, LIDAR, LiFi, and visiblelight communication devices and methods, and various combinations ofabove in applications of general lighting, commercial lighting anddisplay, automotive lighting and communication, defense and security,industrial processing, and internet communications, and others.

As background, while LED-based light sources offer great advantages overincandescent based sources, there are still challenges and limitationsassociated with LED device physics. The first limitation is the socalled “droop” phenomenon that plagues GaN based LEDs. The droop effectleads to power rollover with increased current density, which forcesLEDs to hit peak external quantum efficiency at very low currentdensities in the 10-200 A/cm² range. FIG. 1 shows a schematic diagram ofthe relationship between internal quantum efficiency [IQE] and carrierconcentration in the light emitting layers of a light emitting diode[LED] and light-emitting devices where stimulated emission issignificant such as laser diodes [LDs] or super-luminescent LEDs. IQE isdefined as the ratio of the radiative recombination rate to the totalrecombination rate in the device. At low carrier concentrationsShockley-Reed-Hall recombination at crystal defects dominatesrecombination rates such that IQE is low. At moderate carrierconcentrations, spontaneous radiative recombination dominates such thatIQE is relatively high. At high carrier concentrations, non-radiativeauger recombination dominates such that IQE is again relatively low. Indevices such as LDs or SLEDs, stimulated emission at very high carrierdensities leads to a fourth regime where IQE is relatively high. FIG. 2shows a plot of the external quantum efficiency [EQE] for a typical blueLED and for a high power blue laser diode. EQE is defined as the productof the IQE and the fraction of generated photons that are able to exitthe device. While the blue LED achieves a very high EQE at very lowcurrent densities, it exhibits very low EQE at high current densitiesdue to the dominance of auger recombination at high current densities.The LD, however, is dominated by stimulated emission at high currentdensities, and exhibits very high EQE. At low current densities, the LDhas relatively poor EQE due to re-absorption of photons in the device.Thus, to maximize efficiency of the LED based light source, the currentdensity must be limited to low values where the light output is alsolimited. The result is low output power per unit area of LED die [flux],which forces the use large LED die areas to meet the brightnessrequirements for most applications. For example, a typical LED basedlight bulb will require 3 mm² to 30 mm² of epi area.

A second limitation of LEDs is also related to their brightness, morespecifically it is related to their spatial brightness. A conventionalhigh brightness LED emits ˜1 W per mm² of epi area. With some advancesand breakthrough this can be increased up to 5-10× to 5-10 W per mm² ofepi area. Finally, LEDs fabricated on conventional c-plane GaN sufferfrom strong internal polarization fields, which spatially separate theelectron and hole wave functions and lead to poor radiativerecombination efficiency. Since this phenomenon becomes more pronouncedin InGaN layers with increased indium content for increased wavelengthemission, extending the performance of UV or blue GaN-based LEDs to theblue-green or green regime has been difficult.

An exciting new class of solid-state lighting based on laser diodes israpidly emerging. Like an LED, a laser diode is a two-lead semiconductorlight source that that emits electromagnetic radiation. However, unlikethe output from an LED that is primarily spontaneous emission, theoutput of a laser diode is comprised primarily of stimulated emission.The laser diode contains a gain medium that functions to provideemission through the recombination of electron-hole pairs and a cavityregion that functions as a resonator for the emission from the gainmedium. When a suitable voltage is applied to the leads to sufficientlypump the gain medium, the cavity losses are overcome by the gain and thelaser diode reaches the so-called threshold condition, wherein a steepincrease in the light output versus current input characteristic isobserved. At the threshold condition, the carrier density clamps andstimulated emission dominates the emission. Since the droop phenomenonthat plagues LEDs is dependent on carrier density, the clamped carrierdensity within laser diodes provides a solution to the droop challenge.Further, laser diodes emit highly directional and coherent light withorders of magnitude higher spatial brightness than LEDs. For example, acommercially available edge emitting GaN-based laser diode can reliablyproduce about 2 W of power in an aperture that is 15 μm wide by about0.5 μm tall, which equates to over 250,000 W/mm². This spatialbrightness is over 5 orders of magnitude higher than LEDs or put anotherway, 10,000 times brighter than an LED.

Based on essentially all the pioneering work on GaN LEDs, visible laserdiodes based on GaN technology have rapidly emerged over the past 20years. Currently the only viable direct blue and green laser diodestructures are fabricated from the wurtzite AlGaInN material system. Themanufacturing of light emitting diodes from GaN related materials isdominated by the heteroepitaxial growth of GaN on foreign substratessuch as Si, SiC and sapphire. Laser diode devices operate at such highcurrent densities that the crystalline defects associated withheteroepitaxial growth are not acceptable. Because of this, very lowdefect-density, free-standing GaN substrates have become the substrateof choice for GaN laser diode manufacturing. Unfortunately, such bulkGaN substrates are costly and not widely available in large diameters.For example, 2″ diameter is the most common laser-quality bulk GaNc-plane substrate size today with recent progress enabling 4″ diameter,which are still relatively small compared to the 6″ and greaterdiameters that are commercially available for mature substratetechnologies. Further details of the present invention can be foundthroughout the present specification and more particularly below.

Additional benefits are achieved over pre-existing techniques using thepresent invention. In particular, the present invention enables acost-effective laser-based remotely delivered white light source. In aspecific embodiment, the present optical device can be manufactured in arelatively simple and cost-effective manner. Depending upon theembodiment, the present apparatus and method can be manufactured usingconventional materials and/or methods according to one of ordinary skillin the art. In some embodiments of this invention the gallium andnitrogen containing laser diode source is based on c-plane galliumnitride material and in other embodiments the laser diode is based onnonpolar or semipolar gallium and nitride material. In one embodimentthe white source is configured from a laser chip on submount (CoS) withthe laser light being delivered by a waveguide to a phosphor supportedon a remotely disposed submount and/or a remote support member to form aremotely-delivered white light source. In some embodiments, thewaveguide is a semiconductor waveguide integrated on a intermediatesubmount coupled with the CoS. In some embodiments the waveguideincludes an optical fiber disposed substantially free in space or incustom layout, making the white light source a fiber-delivered whitelight source. In some embodiments the white light source includes beamcollimation and focus elements to couple the laser light into thewaveguide or fiber. In some embodiments, the white light source includesmultiple laser chips either independently or co-packaged in a samepackage caseand the phosphor member are supported in a separate submontheatsink packaged in a remote case. In some embodiments there could beadditional beam shaping optical elements included for shaping orcontrolling the white light out of the phosphor.

In various embodiments, the laser device and phosphor device areseparately packaged or mounted on respective support member and thephosphor materials are operated in a reflective mode to result in awhite emitting laser-based light source. In additional variousembodiments, the electromagnetic radiation from the laser device isremotely coupled to the phosphor device through means such as free spacecoupling or coupling with a waveguide such as a fiber optic cable orother solid waveguide material, and wherein the phosphor materials areoperated in a reflective mode to result in a white emitting laser-basedlight source. Merely by way of example, the invention can be applied toapplications such as white lighting, white spot lighting, flash lights,automobile headlights, all-terrain vehicle lighting, flash sources suchas camera flashes, light sources used in recreational sports such asbiking, surfing, running, racing, boating, light sources used fordrones, planes, robots, other mobile or robotic applications, safety,counter measures in defense applications, multi-colored lighting,lighting for flat panels, medical, metrology, beam projectors and otherdisplays, high intensity lamps, spectroscopy, entertainment, theater,music, and concerts, analysis fraud detection and/or authenticating,tools, water treatment, laser dazzlers, targeting, communications, LiFi,visible light communications (VLC), sensing, detecting, distancedetecting, Light Detection And Ranging (LIDAR), transformations,autonomous vehicles, transportations, leveling, curing and otherchemical treatments, heating, cutting and/or ablating, pumping otheroptical devices, other optoelectronic devices and related applications,and source lighting and the like.

Laser diodes are ideal as phosphor excitation sources. With a spatialbrightness (optical intensity per unit area) greater than 10,000 timeshigher than conventional LEDs and the extreme directionality of thelaser emission, laser diodes enable characteristics unachievable by LEDsand other light sources. Specifically, since the laser diodes outputbeams carrying over 1 W, over 5 W, over 10 W, or even over 100 W can befocused to very small spot sizes of less than 1 mm in diameter, lessthan 500 μm in diameter, less than 100 μm in diameter, or even less than50 μm in diameter, power densities of over 1 W/mm², 100 W/mm², or evenover 2,500 W/mm² can be achieved. When this very small and powerful beamof laser excitation light is incident on a phosphor material theultimate point source of white light can be achieved. Assuming aphosphor conversion ratio of 200 lumens of emitted white light peroptical watt of excitation light, a 5 W excitation power could generate1000 lumens in a beam diameter of 100 μm, or 50 μm, or less. Such apoint source is game changing in applications such as spotlighting orrange finding where parabolic reflectors or lensing optics can becombined with the point source to create highly collimated white lightspots that can travel drastically higher distances than ever possiblebefore using LEDs or bulb technology.

In some embodiments of the present invention the gallium and nitrogencontaining light emitting device may not be a laser device, but insteadmay be configured as a superluminescent diode or superluminescent lightemitting diode (SLED) device. For the purposes of this invention, a SLEDdevice and laser diode device can be used interchangeably. A SLED issimilar to a laser diode as it is based on an electrically drivenjunction that when injected with current becomes optically active andgenerates amplified spontaneous emission (ASE) and gain over a widerange of wavelengths. When the optical output becomes dominated by ASEthere is a knee in the light output versus current (LI) characteristicwherein the unit of light output becomes drastically larger per unit ofinjected current. This knee in the LI curve resembles the threshold of alaser diode, but is much softer. The advantage of a SLED device is thatSLED it can combine the unique properties of high optical emission powerand extremely high spatial brightness of laser diodes that make themideal for highly efficient long throw illumination and high brightnessphosphor excitation applications with a broad spectral width of (>5 nm)that provides for an improved eye safety and image quality in somecases. The broad spectral width results in a low coherence lengthsimilar to an LED. The low coherence length provides for an improvedsafety such has improved eye safety. Moreover, the broad spectral widthcan drastically reduce optical distortions in display or illuminationapplications. As an example, the well-known distortion pattern referredto as “speckle” is the result of an intensity pattern produced by themutual interference of a set of wavefronts on a surface or in a viewingplane. The general equations typically used to quantify the degree ofspeckle are inversely proportional to the spectral width. In the presentspecification, both a laser diode (LD) device and a superluminescentlight emitting diode (SLED) device are sometime simply referred to“laser device”.

A gallium and nitrogen containing laser diode (LD) or super luminescentlight emitting diode (SLED) may comprise at least a gallium and nitrogencontaining device having an active region and a cavity member and arecharacterized by emitted spectra generated by the stimulated emission ofphotons. In some embodiments a laser device emitting red laser light,i.e. light with wavelength between about 600 nm to 750 nm, are provided.These red laser diodes may comprise at least a gallium phosphorus andarsenic containing device having an active region and a cavity memberand are characterized by emitted spectra generated by the stimulatedemission of photons. The ideal wavelength for a red device for displayapplications is ˜635 nm, for green ˜530 nm and for blue 440-470 nm.There may be tradeoffs between what colors are rendered with a displayusing different wavelength lasers and also how bright the display is asthe eye is more sensitive to some wavelengths than to others.

In some embodiments according to the present invention, multiple laserdiode sources are configured to excite the same phosphor or phosphornetwork. Combining multiple laser sources can offer many potentialbenefits according to this invention. First, the excitation power can beincreased by beam combining to provide a more powerful excitation spitand hence produce a brighter light source. In some embodiments, separateindividual laser chips are configured within the laser-phosphor lightsource. By including multiple lasers emitting 1 W, 2 W, 3 W, 4 W, 5 W ormore power each, the excitation power can be increased and hence thesource brightness would be increased. For example, by including two 3 Wlasers exciting the same phosphor area, the excitation power can beincreased to 6 W for double the white light brightness. In an examplewhere about 200 lumens of white are generated per 1 watt of laserexcitation power, the white light output would be increased from 600lumens to 1200 lumens. Beyond scaling the power of each single laserdiode emitter, the total luminous flux of the white light source can beincreased by continuing to increase the total number of laser diodes,which can range from 10s, to 100s, and even to 1000s of laser diodeemitters resulting in 10s to 100s of kW of laser diode excitation power.Scaling the number of laser diode emitters can be accomplished in manyways such as including multiple lasers in a co-package, spatial beamcombining through conventional refractive optics or polarizationcombining, and others. Moreover, laser diode bars or arrays, andmini-bars can be utilized where each laser chip includes many adjacentlaser diode emitters. For example, a bar could include from 2 to 100laser diode emitters spaced from about 10 microns to about 400 micronsapart. Similarly, the reliability of the source can be increased byusing multiple sources at lower drive conditions to achieve the sameexcitation power as a single source driven at more harsh conditions suchas higher current and voltage.

In a specific area of light source application is automobile headlamp.Semiconductor based light emitting diode (LED) headlight sources werefielded in 2004, the first solid-state sources. These featured highefficiency, reliability, and compactness, but the limited light outputper device and brightness caused the optics and heat sinks to be stillare quite large, and the elevated temperature requirements in autoapplications were challenging. Color uniformity from the blue LEDexcited yellow phosphor needed managed with special reflector design.Single LED failure meant the entire headlamp needed to be scrapped,resulting in challenging costs for maintenance, repair, and warranty.Moreover, the LED components are based on spontaneous emission, andtherefore are not conducive to high-speed modulation required foradvanced applications such as 3D sensing (LiDAR), or opticalcommunication (LiFi). The low luminance also creates challenges forspatially dynamic automotive lighting systems that utilize spatialmodulators such as MEMS or liquid crystal devices. Semiconductor laserdiode (LD) based headlights started production in 2014 based on laserpumped phosphor architectures, since direct emitting lasers such asR-G-B lasers are not safe to deploy onto the road and since R-G-Bsources leave gaps in the spectrum that would leave common roadsidetargets such as yellow or orange with insufficient reflection back tothe eye. Laser pumped phosphor are solid state light sources andtherefore featured the same benefits of LEDs, but with higher brightnessand range from more compact headlamp reflectors. Initially, thesesources exhibited high costs, reduced reliability compared to LEDs, dueto being newer technology. In some cases, the laser and phosphor werecombined in a single unit, and in other cases, the blue laser light wasdelivered by fiber to a remotely disposed phosphor module to producewhite light emission. Special precautions were needed to ensure safewhite light emission occurred with passive and active safety measures.Color uniformity from the blue laser excited yellow phosphor neededmanaged with special reflector design.

In some embodiments, the invention described herein can be applied to afiber delivered headlight comprised of one or more gallium and nitrogencontaining visible laser diode for emitting laser light that isefficiently coupled into a waveguide (such as an optical fiber) todeliver the laser emission to a remote phosphor member configured on theother end of the optical fiber. The laser emission serves to excite thephosphor member and generate a high brightness white light. In aheadlight application, the phosphor member and white light generationoccurs in a final headlight module, from where the light is collimatedand shaped onto the road to achieve the desired light pattern.

This disclosure utilizes fiber delivery of visible laser light from agallium and nitrogen containing laser diode to a remote phosphor memberto generate a white light emission with high luminance, and has severalkey benefits over other approaches. One advantage lies in production ofcontrollable light output or amount of light for low beam or high beamusing modular design in a miniature headlight module footprint. Anotheradvantage is to provide high luminance and long range of visibility. Forexample, based on recent driving speeds and safe stopping distances, arange of 800 meters to 1 km is possible from a 200 lumens on the roadusing a size<35 mm optic structure with light sources that are 1000 cdper mm². Using higher luminance light sources allows one to achievelonger-range visibility for the same optics size. Further advantage ofthe fiber-delivered white-light headlight is able to provide highcontrast. It is important to minimize glare and maximize safety andvisibility for drivers and others including oncoming traffic,pedestrians, animals, and drivers headed in the same direction trafficahead. High luminance is required to produce sharp light gradients andthe specific regulated light patterns for automotive lighting. Moreover,using a waveguide such as an optical fiber, extremely sharp lightgradients and ultra-safe glare reduction can be generated by reshapingand projecting the decisive light cutoff that exists from core tocladding in the light emission profile.

Another advantage of the present invention is to provide rich spectrumwhite color light. Laser pumped phosphors are broadband solid-statelight sources and therefore featured the same benefits of LEDs, but withhigher luminance. Direct emitting lasers such as R-G-B lasers are notsafe to deploy onto the road since R-G-B sources leave gaps in thespectrum that would leave common roadside targets such as yellow ororange with insufficient reflection back to the eye. Also, because ofthe remote nature of the light sources, the headlight module can bemounted onto a pre-existing heat sink with adequate thermal mass that islocated anywhere in the vehicle, eliminating the need for heat sink inthe headlight.

One big advantage is small form factor of the light source and alow-cost solution for swiveling the light for glare mitigation andenhancing aerodynamic performance. For example, miniature optics <1 cmin diameter in a headlight module can be utilized to capture nearly 100%of the light from the fiber. The white light can be collimated andshaped with tiny diffusers or simple optical elements to produce thedesired beam pattern on the road. it is desired to have extremely smalloptics sizes for styling of the vehicle. Using higher luminance lightsources allows one to achieve smaller optics sizes for the same range ofvisibility. This headlight design allows one to integrate the headlightmodule into the grill, onto wheel cover, into seams between the hood andfront bumper, etc. This headlight design features a headlight modulethat is extremely low mass and lightweight, and therefore minimizedweight in the front of the car, contributing to safety, fuel economy,and speed/acceleration performance. For electric vehicles, thistranslates to increased vehicle range. Moreover, the decoupled fiberdelivered architecture use pre-existing heat sink thermal mass alreadyin vehicle, further minimizing the weight in the car. Furthermore, thisheadlight module is based on solid-state light source, and has longlifetime >10,000 hours. Redundancy and interchangeability arestraightforward by simply replacing the fiber-delivered laser lightsource.

Because of the fiber configuration in the design of the fiber-deliveredlaser-induced white light headlight module, reliability is maximized bypositioning the laser-induced light source away from the hot area nearengine and other heat producing components. This allows the headlightmodule to operate at extremely high temperatures >100° C., while thelaser module can operate in a cool spot with ample heat sinking. In aspecific embodiment, the present invention utilizes thermally stable,military standard style, telcordia type packaging technology. The onlyelements exposed to the front of the car are the complexly passiveheadlight module, comprised tiny macro-optical elements. There is nolaser directly deployed in the headlight module, only incoherent whitelight and a reflective phosphor architecture inside. Direct emittinglasers such as R-G-B lasers are not safe to deploy onto the road at highpower and are not used in this design. It is safe and cost efficient toassemble this fiber-delivered white light source into the car whilemanufacturing the vehicle.

In LED-based headlights, if one high power LED element dies, the entireheadlamp is typically scrapped. The fiber-delivered headlight designenables “plug and play” replacement of the light source, eliminatingwasted action of completely scrapping headlights due to a failedcomponent. The plug and play can occur without alignment, like replacinga battery, minimize warranty costs. This eliminates excessivereplacement cost, customer wait times, dangerous driving conditions, andexpensive loaner vehicles. Because of the ease of generating new lightpatterns, and the modular approach to lumen scaling, thisfiber-delivered light source allows for changing lumens and beam patternfor any region without retooling for an entirely new headlamp. Thisconvenient capability to change beam pattern can be achieved by changingtiny optics and or diffusers instead of retooling for new largereflectors. Moreover, the fiber-delivered white light source can be usedin interior lights and daytime running lights (DRL), with transport orside emitting plastic optical fiber (POF).

Spatially dynamic beam shaping devices such as digital-light processing(DLP), liquid-crystal display (LCD), 1 or 2 MEMS or Galvo mirrorsystems, lightweight swivels, scanning fiber tips. Future spatiallydynamic sources may require even brighter light, such as 5000-10000lumens from the source, to produce high definition spatial lightmodulation on the road using MEMS or liquid crystal components. Suchdynamic lighting systems are incredibly bulky and expensive whenco-locating the light source, electronics, heat sink, optics, and lightmodulators, and secondary optics. Therefore, they require-fiberdelivered high luminance white light to enable spatial light modulationin a compact and more cost effective manner.

A additional advantage of combining the emission from multiple laserdiode emitters is the potential for a more circular spot by rotating thefirst free space diverging elliptical laser beam by 90 degrees relativeto the second free space diverging elliptical laser beam and overlappingthe centered ellipses on the phosphor. Alternatively, a more circularspot can be achieved by rotating the first free space divergingelliptical laser beam by 180 degrees relative to the second free spacediverging elliptical laser beam and off-centered overlapping theellipses on the phosphor to increase spot diameter in slow axisdiverging direction. In another configuration, more than 2 lasers areincluded and some combination of the above described beam shaping spotgeometry shaping is achieved. A third and important advantage is thatmultiple color lasers in an emitting device can significantly improvecolor quality (CRI and CQS) by improving the fill of the spectra in theviolet/blue and cyan region of the visible spectrum. For example, two ormore blue excitation lasers with slightly detuned wavelengths (e.g. 5nm, 10 nm, 15 nm, etc.) can be included to excite a yellow phosphor andcreate a larger blue spectrum.

As used herein, the term GaN substrate is associated with GroupIII-nitride based materials including GaN, InGaN, AlGaN, or other GroupIII containing alloys or compositions that are used as startingmaterials. Such starting materials include polar GaN substrates (i.e.,substrate where the largest area surface is nominally an (h k l) planewherein h=k=0, and 1 is non-zero), non-polar GaN substrates (i.e.,substrate material where the largest area surface is oriented at anangle ranging from about 80-100 degrees from the polar orientationdescribed above towards an (h k l) plane wherein l=0, and at least oneof h and k is non-zero) or semi-polar GaN substrates (i.e., substratematerial where the largest area surface is oriented at an angle rangingfrom about +0.1 to 80 degrees or 110-179.9 degrees from the polarorientation described above towards an (h k l) plane wherein l=0, and atleast one of h and k is non-zero). Of course, there can be othervariations, modifications, and alternatives.

The laser diode device can be fabricated on a conventional orientationof a gallium and nitrogen containing film or substrate (e.g., GaN) suchas the polar c-plane, on a nonpolar orientation such as the m-plane, oron a semipolar orientation such as the {30-31}, {20-21}, {30-32},{11-22}, {10-11}, {30-3-1}, {20-2-1}, {30-3-2}, or offcuts of any ofthese polar, nonpolar, and semipolar planes within +/−10 degrees towardsa c-plane, and/or +/−10 degrees towards an a-plane, and/or +/−10 degreestowards an m-plane. In some embodiments, a gallium and nitrogencontaining laser diode laser diode comprises a gallium and nitrogencontaining substrate. The substrate member may have a surface region onthe polar {0001} plane (c-plane), nonpolar plane (m-plane, a-plane), andsemipolar plain ({11-22}, {10-1-1}, {20-21}, {30-31}) or other planes ofa gallium and nitrogen containing substrate. The laser device can beconfigured to emit a laser beam characterized by one or more wavelengthsfrom about 390 nm to about 540 nm.

FIG. 3 is a simplified schematic diagram of a laser diode formed on agallium and nitrogen containing substrate with the cavity aligned in adirection ended with cleaved or etched mirrors according to someembodiments of the present invention. In an example, the substratesurface 101 is a polar c-plane and the laser stripe region 110 ischaracterized by a cavity orientation substantially in an m-direction10, which is substantially normal to an a-direction 20, but can beothers such as cavity alignment substantially in the a-direction. Thelaser strip region 110 has a first end 107 and a second end 109 and isformed on an m-direction on a {0001} gallium and nitrogen containingsubstrate having a pair of cleaved or etched mirror structures, whichface each other. In another example, the substrate surface 101 is asemipolar plane and the laser stripe region 110 is characterized by acavity orientation substantially in a projection of a c-direction 10,which is substantially normal to an a-direction 20, but can be otherssuch as cavity alignment substantially in the a-direction. The laserstrip region 110 has a first end 107 and a second end 109 and is formedon an semipolar substrate such as a {40-41}, {30-31}, {20-21}, {40-4-1},{30-3-1}, {20-2-1}, {20-21}, or an offcut of these planes within +/−5degrees from the c-plane and a-plane gallium and nitrogen containingsubstrate. Optionally, the gallium nitride substrate member is a bulkGaN substrate characterized by having a nonpolar or semipolarcrystalline surface region, but can be others. The bulk GaN substratemay have a surface dislocation density below 10⁵ cm⁻² or 10⁵ to 10⁷cm⁻². The nitride crystal or wafer may comprise Al_(x)In_(y)Ga_(1-x-y)N,where 0≤x, y, x+y≤1. In one specific embodiment, the nitride crystalcomprises GaN. In some embodiments, the GaN substrate has threadingdislocations, at a concentration between about 10⁵ cm⁻² and about 10⁸cm⁻², in a direction that is substantially orthogonal or oblique withrespect to the surface.

The exemplary laser diode devices in FIG. 3 have a pair of cleaved oretched mirror structures 109 and 107, which face each other. The firstcleaved or etched facet 109 comprises a reflective coating and thesecond cleaved or etched facet 107 comprises no coating, anantireflective coating, or exposes gallium and nitrogen containingmaterial. The first cleaved or etched facet 109 is substantiallyparallel with the second cleaved or etched facet 107. The first andsecond cleaved facets 109 and 107 are provided by a scribing andbreaking process according to an embodiment or alternatively by etchingtechniques using etching technologies such as reactive ion etching (ME),inductively coupled plasma etching (ICP), or chemical assisted ion beametching (CAIBE), or other method. The reflective coating is selectedfrom silicon dioxide, hafnia, and titania, tantalum pentoxide, zirconia,aluminum oxide, aluminum nitride, and aluminum oxynitride includingcombinations, and the like. Depending upon the design, the mirrorsurfaces can also comprise an anti-reflective coating.

In a specific embodiment, the method of facet formation includessubjecting the substrates to a laser for pattern formation. In apreferred embodiment, the pattern is configured for the formation of apair of facets for a ridge laser. In a preferred embodiment, the pair offacets face each other and are in parallel alignment with each other. Ina preferred embodiment, the method uses a UV (355 nm) laser to scribethe laser bars. In a specific embodiment, the laser is configured on asystem, which allows for accurate scribe lines configured in a differentpatterns and profiles. In some embodiments, the laser scribing can beperformed on the back-side, front-side, or both depending upon theapplication. Of course, there can be other variations, modifications,and alternatives.

In a specific embodiment, the method uses backside laser scribing or thelike. With backside laser scribing, the method preferably forms acontinuous line laser scribe that is perpendicular to the laser bars onthe backside of the GaN substrate. In a specific embodiment, the laserscribe is generally about 15-20 μm deep or other suitable depth.Preferably, backside scribing can be advantageous. That is, the laserscribe process does not depend on the pitch of the laser bars or otherlike pattern. Accordingly, backside laser scribing can lead to a higherdensity of laser bars on each substrate according to a preferredembodiment. In a specific embodiment, backside laser scribing, however,may lead to residue from the tape on the facets. In a specificembodiment, backside laser scribe often requires that the substratesface down on the tape. With front-side laser scribing, the backside ofthe substrate is in contact with the tape. Of course, there can be othervariations, modifications, and alternatives.

It is well known that etch techniques such as chemical assisted ion beametching (CAIBE), inductively coupled plasma (ICP) etching, or reactiveion etching (RIE) can result in smooth and vertical etched sidewallregions, which could serve as facets in etched facet laser diodes. Inthe etched facet process a masking layer is deposited and patterned onthe surface of the wafer. The etch mask layer could be comprised ofdielectrics such as silicon dioxide (SiO₂), silicon nitride(Si_(x)N_(y)), a combination thereof or other dielectric materials.Further, the mask layer could be comprised of metal layers such as Ni orCr, but could be comprised of metal combination stacks or stackscomprising metal and dielectrics. In another approach, photoresist maskscan be used either alone or in combination with dielectrics and/ormetals. The etch mask layer is patterned using conventionalphotolithography and etch steps. The alignment lithography could beperformed with a contact aligner or stepper aligner. Suchlithographically defined mirrors provide a high level of control to thedesign engineer. After patterning of the photoresist mask on top of theetch mask is complete, the patterns in then transferred to the etch maskusing a wet etch or dry etch technique. Finally, the facet pattern isthen etched into the wafer using a dry etching technique selected fromCAIBE, ICP, RIE and/or other techniques. The etched facet surfaces mustbe highly vertical of between about 87 and about 93 degrees or betweenabout 89 and about 91 degrees from the surface plane of the wafer. Theetched facet surface region must be very smooth with root mean squareroughness values of less than about 50 nm, 20 nm, 5 nm, or 1 nm. Lastly,the etched must be substantially free from damage, which could act asnonradiative recombination centers and hence reduce the catastrophicoptical mirror damage (COMD) threshold. CAIBE is known to provide verysmooth and low damage sidewalls due to the chemical nature of the etch,while it can provide highly vertical etches due to the ability to tiltthe wafer stage to compensate for any inherent angle in etch.

The laser stripe 110 is characterized by a length and width. The lengthranges from about 50 μm to about 3000 μm, but is preferably betweenabout 10 μm and about 400 μm, between about 400 μm and about 800 μm, orabout 800 μm and about 1600 μm, but could be others. The stripe also hasa width ranging from about 0.5 μm to about 50 μm, but is preferablybetween about 0.8 μm and about 2.5 μm for single lateral mode operationor between about 2.5 μm and about 50 μm for multi-lateral modeoperation, but can be other dimensions. In a specific embodiment, thepresent device has a width ranging from about 0.5 μm to about 1.5 μm, awidth ranging from about 1.5 μm to about 3.0 μm, a width ranging fromabout 3.0 μm to about 50 μm, and others. In a specific embodiment, thewidth is substantially constant in dimension, although there may beslight variations. The width and length are often formed using a maskingand etching process, which are commonly used in the art.

The laser stripe region 110 is provided by an etching process selectedfrom dry etching or wet etching. The device also has an overlyingdielectric region, which exposes a p-type contact region. Overlying thecontact region is a contact material, which may be metal or a conductiveoxide or a combination thereof. The p-type electrical contact may bedeposited by thermal evaporation, electron beam evaporation,electroplating, sputtering, or another suitable technique. Overlying thepolished region of the substrate is a second contact material, which maybe metal or a conductive oxide or a combination thereof and whichcomprises the n-type electrical contact. The n-type electrical contactmay be deposited by thermal evaporation, electron beam evaporation,electroplating, sputtering, or another suitable technique.

In a specific embodiment, the laser device may emit red light with acenter wavelength between 600 nm and 750 nm. Such a device may compriselayers of varying compositions of Al_(x)In_(y)Ga_(1-x-y)As_(z)P_(1-z),where x+y≤1 and z≤1. The red laser device comprises at least an n-typeand p-type cladding layer, an n-type SCH of higher refractive index thanthe n-type cladding, a p-type SCH of higher refractive index than thep-type cladding and an active region where light is emitted. In aspecific embodiment, the laser stripe is provided by an etching processselected from dry etching or wet etching. In a preferred embodiment, theetching process is dry, but can be others. The device also has anoverlying dielectric region, which exposes the contact region. In aspecific embodiment, the dielectric region is an oxide such as silicondioxide, but can be others. Of course, there can be other variations,modifications, and alternatives. The laser stripe is characterized by alength and width. The length ranges from about 50 μm to about 3000 μm,but is preferably between 10 μm and 400 μm, between about 400 μm and 800μm, or about 800 μm and 1600 μm, but could be others such as greaterthan 1600 μm. The stripe also has a width ranging from about 0.5 μm toabout 80 μm, but is preferably between 0.8 μm and 2.5 μm for singlelateral mode operation or between 2.5 μm and 60 μm for multi-lateralmode operation, but can be other dimensions. The laser strip region hasa first end and a second end having a pair of cleaved or etched mirrorstructures, which face each other. The first facet comprises areflective coating and the second facet comprises no coating, anantireflective coating, or exposes gallium and nitrogen containingmaterial. The first facet is substantially parallel with the secondcleaved or etched facet.

Given the high gallium and nitrogen containing substrate costs,difficulty in scaling up gallium and nitrogen containing substrate size,the inefficiencies inherent in the processing of small wafers, andpotential supply limitations it becomes extremely desirable to maximizeutilization of available gallium and nitrogen containing substrate andoverlying epitaxial material. In the fabrication of lateral cavity laserdiodes, it is typically the case that minimum die size is determined bydevice components such as the wire bonding pads or mechanical handlingconsiderations, rather than by laser cavity widths. Minimizing die sizeis critical to reducing manufacturing costs as smaller die sizes allow agreater number of devices to be fabricated on a single wafer in a singleprocessing run. The current invention is a method of maximizing thenumber of devices which can be fabricated from a given gallium andnitrogen containing substrate and overlying epitaxial material byspreading out the epitaxial material onto a carrier wafer via a dieexpansion process.

Similar to an edge emitting laser diode, a SLED is typically configuredas an edge-emitting device wherein the high brightness, highlydirectional optical emission exits a waveguide directed outward from theside of the semiconductor chip. SLEDs are designed to have high singlepass gain or amplification for the spontaneous emission generated alongthe waveguide. However, unlike laser diodes, they are designed toprovide insufficient feedback to in the cavity to achieve the lasingcondition where the gain equals the total losses in the waveguidecavity. In a typical example, at least one of the waveguide ends orfacets is designed to provide very low reflectivity back into thewaveguide. Several methods can be used to achieve reduced reflectivityon the waveguide end or facet. In one approach an optical coating isapplied to at least one of the facets, wherein the optical coating isdesigned for low reflectivity such as less than 1%, less than 0.1%, lessthan 0.001%, or less than 0.0001% reflectivity. In another approach forreduced reflectivity the waveguide ends are designed to be tilted orangled with respect to the direction of light propagation such that thelight that is reflected back into the chip does not constructivelyinterfere with the light in the cavity to provide feedback. The tiltangle must be carefully designed around a null in the reflectivityversus angle relationship for optimum performance. The tilted or angledfacet approach can be achieved in a number of ways including providingan etched facet that is designed with an optimized angle lateral anglewith respect to the direction of light propagation. The angle of thetilt is pre-determined by the lithographically defined etched facetpatter. Alternatively, the angled output could be achieved by curvingand/or angling the waveguide with respect to a cleaved facet that formson a pre-determined crystallographic plane in the semiconductor chip.Another approach to reduce the reflectivity is to provide a roughened orpatterned surface on the facet to reduce the feedback to the cavity. Theroughening could be achieved using chemical etching and/or a dryetching, or with an alternative technique. Of course, there may be othermethods for reduced feedback to the cavity to form a SLED device. Inmany embodiments a number of techniques can be used in combination toreduce the facet reflectivity including using low reflectivity coatingsin combination with angled or tilted output facets with respect to thelight propagation.

In a specific embodiment on a nonpolar Ga-containing substrate, thedevice is characterized by a spontaneously emitted light is polarized insubstantially perpendicular to the c-direction. In a preferredembodiment, the spontaneously emitted light is characterized by apolarization ratio of greater than 0.1 to about 1 perpendicular to thec-direction. In a preferred embodiment, the spontaneously emitted lightcharacterized by a wavelength ranging from about 430 nanometers to about470 nm to yield a blue emission, or about 500 nanometers to about 540nanometers to yield a green emission, and others. For example, thespontaneously emitted light can be violet (e.g., 395 to 420 nanometers),blue (e.g., 420 to 470 nm); green (e.g., 500 to 540 nm), or others. In apreferred embodiment, the spontaneously emitted light is highlypolarized and is characterized by a polarization ratio of greater than0.4. In another specific embodiment on a semipolar {20-21} Ga-containingsubstrate, the device is also characterized by a spontaneously emittedlight is polarized in substantially parallel to the a-direction orperpendicular to the cavity direction, which is oriented in theprojection of the c-direction.

In a specific embodiment, the present invention provides an alternativedevice structure capable of emitting 501 nm and greater light in a ridgelaser embodiment. The device is provided with a of the followingepitaxially grown elements:

-   -   an n-GaN or n-AlGaN cladding layer with a thickness from 100 nm        to 3000 nm with Si doping level of 5×10¹⁷ cm⁻³ to 3×10¹⁸ cm⁻³;    -   an n-side SCH layer comprised of InGaN with molar fraction of        indium of between 2% and 15% and thickness from 20 nm to 250 nm;    -   a single quantum well or a multiple quantum well active region        comprised of at least two 2.0 nm to 8.5 nm InGaN quantum wells        separated by 1.5 nm and greater, and optionally up to about 12        nm, GaN or InGaN barriers;    -   a p-side SCH layer comprised of InGaN with molar a fraction of        indium of between 1% and 10% and a thickness from 15 nm to 250        nm or an upper GaN-guide layer;    -   an electron blocking layer comprised of AlGaN with molar        fraction of aluminum of between 0% and 22% and thickness from 5        nm to 20 nm and doped with Mg;    -   a p-GaN or p-AlGaN cladding layer with a thickness from 400 nm        to 1500 nm with Mg doping level of 2×10¹⁷ cm⁻³ to 2×10¹⁹ cm-3;        and    -   a p⁺⁺-GaN contact layer with a thickness from 20 nm to 40 nm        with Mg doping level of 1×10¹⁹ cm⁻³ to 1×10²¹ cm⁻³.

A gallium and nitrogen containing laser diode laser device may alsoinclude other structures, such as a surface ridge architecture, a buriedheterostructure architecture, and/or a plurality of metal electrodes forselectively exciting the active region. For example, the active regionmay comprise first and second gallium and nitrogen containing claddinglayers and an indium and gallium containing emitting layer positionedbetween the first and second cladding layers. A laser device may furtherinclude an n-type gallium and nitrogen containing material and an n-typecladding material overlying the n-type gallium and nitrogen containingmaterial. In a specific embodiment, the device also has an overlyingn-type gallium nitride layer, an active region, and an overlying p-typegallium nitride layer structured as a laser stripe region. Additionally,the device may also include an n-side separate confinementheterostructure (SCH), p-side guiding layer or SCH, p-AlGaN EBL, amongother features. In a specific embodiment, the device also has a p++ typegallium nitride material to form a contact region. In a specificembodiment, the p++ type contact region has a suitable thickness and mayrange from about 10 nm 50 nm, or other thicknesses. In a specificembodiment, the doping level can be higher than the p-type claddingregion and/or bulk region. In a specific embodiment, the p++ type regionhas doping concentration ranging from about 10¹⁹ to 10²¹ Mg/am³, andothers. The p++ type region preferably causes tunneling between thesemiconductor region and overlying metal contact region. In a specificembodiment, each of these regions is formed using at least an epitaxialdeposition technique of metal organic chemical vapor deposition (MOCVD),molecular beam epitaxy (MBE), or other epitaxial growth techniquessuitable for GaN growth. In a specific embodiment, the epitaxial layeris a high-quality epitaxial layer overlying the n-type gallium nitridelayer. In some embodiments the high-quality layer is doped, for example,with Si or O to form n-type material, with a dopant concentrationbetween about 10¹⁶ cm⁻³ and 10²⁰ cm⁻³.

FIG. 4 is a cross-sectional view of a laser device 200 according to someembodiments of the present disclosure. As shown, the laser deviceincludes gallium nitride substrate 203, which has an underlying n-typemetal back contact region 201. For example, the substrate 203 may becharacterized by a semipolar or nonpolar orientation. The device alsohas an overlying n-type gallium nitride layer 205, an active region 207,and an overlying p-type gallium nitride layer structured as a laserstripe region 209. Each of these regions is formed using at least anepitaxial deposition technique of metal organic chemical vapordeposition (MOCVD), molecular beam epitaxy (MBE), or other epitaxialgrowth techniques suitable for GaN growth. The epitaxial layer is ahigh-quality epitaxial layer overlying the n-type gallium nitride layer.In some embodiments the high-quality layer is doped, for example, withSi or O to form n-type material, with a dopant concentration betweenabout 10¹⁶ cm⁻³ and 10²⁰ cm⁻³.

An n-type Al_(n)In_(v)Ga_(1-u-v)N layer, where 0≤u, v, u+v≤1, isdeposited on the substrate. The carrier concentration may lie in therange between about 10¹⁶ cm⁻³ and 10²⁰ cm⁻³. The deposition may beperformed using metalorganic chemical vapor deposition (MOCVD) ormolecular beam epitaxy (MBE).

For example, the bulk GaN substrate is placed on a susceptor in an MOCVDreactor. After closing, evacuating, and back-filling the reactor (orusing a load lock configuration) to atmospheric pressure, the susceptoris heated to a temperature between about 1000 and about 1200 degreesCelsius in the presence of a nitrogen-containing gas. The susceptor isheated to approximately 900 to 1200 degrees Celsius under flowingammonia. A flow of a gallium-containing metalorganic precursor, such astrimethylgallium (TMG) or triethylgallium (TEG) is initiated, in acarrier gas, at a total rate between approximately 1 and 50 standardcubic centimeters per minute (sccm). The carrier gas may comprisehydrogen, helium, nitrogen, or argon. The ratio of the flow rate of thegroup V precursor (ammonia) to that of the group III precursor(trimethylgallium, triethylgallium, trimethylindium, trimethylaluminum)during growth is between about 2000 and about 12000. A flow of disilanein a carrier gas, with a total flow rate of between about 0.1 sccm and10 sccm, is initiated.

In one embodiment, the laser stripe region is p-type gallium nitridelayer 209. The laser stripe is provided by a dry etching process, butwet etching can be used. The dry etching process is an inductivelycoupled process using chlorine bearing species or a reactive ion etchingprocess using similar chemistries. The chlorine bearing species arecommonly derived from chlorine gas or the like. The device also has anoverlying dielectric region, which exposes a contact region 213. Thedielectric region is an oxide such as silicon dioxide or siliconnitride, and a contact region is coupled to an overlying metal layer215. The overlying metal layer is preferably a multilayered structurecontaining gold and platinum (Pt/Au), palladium and gold (Pd/Au), ornickel gold (Ni/Au), or a combination thereof. In some embodiments,barrier layers and more complex metal stacks are included.

Active region 207 preferably includes one to ten quantum-well regions ora double heterostructure region for light emission. Following depositionof the n-type layer to achieve a desired thickness, an active layer isdeposited. The quantum wells are preferably InGaN with GaN, AlGaN,InAlGaN, or InGaN barrier layers separating them. In other embodiments,the well layers and barrier layers comprise Al_(w)In_(x)Ga_(1-w-x)N andAl_(y)In_(z)Ga_(1-y-z)N, respectively, where 0≤w, x, y, z, w+x, y+z≤1,where w<u, y and/or x>v, z so that the bandgap of the well layer(s) isless than that of the barrier layer(s) and the n-type layer. The welllayers and barrier layers each have a thickness between about 1 nm andabout 20 nm. The composition and structure of the active layer arechosen to provide light emission at a preselected wavelength. The activelayer may be left undoped (or unintentionally doped) or may be dopedn-type or p-type.

The active region can also include an electron blocking region, and aseparate confinement heterostructure. The electron-blocking layer maycomprise Al_(s)In_(t)Ga_(1-s-t)N, where 0≤s, t, s+t≤1, with a higherbandgap than the active layer, and may be doped p-type. In one specificembodiment, the electron blocking layer includes AlGaN. In anotherembodiment, the electron blocking layer includes an AlGaN/GaNsuper-lattice structure, comprising alternating layers of AlGaN and GaN,each with a thickness between about 0.2 nm and about 5 nm.

As noted, the p-type gallium nitride or aluminum gallium nitridestructure is deposited above the electron blocking layer and activelayer(s). The p-type layer may be doped with Mg, to a level betweenabout 10¹⁶ cm⁻³ and 10²² cm⁻³, with a thickness between about 5 nm andabout 1000 nm. The outermost 1-50 nm of the p-type layer may be dopedmore heavily than the rest of the layer, so as to enable an improvedelectrical contact. The device also has an overlying dielectric region,for example, silicon dioxide, which exposes the contact region 213.

The metal contact is made of suitable material such as silver, gold,aluminum, nickel, platinum, rhodium, palladium, chromium, or the like.The contact may be deposited by thermal evaporation, electron beamevaporation, electroplating, sputtering, or another suitable technique.In a preferred embodiment, the electrical contact serves as a p-typeelectrode for the optical device. In another embodiment, the electricalcontact serves as an n-type electrode for the optical device. The laserdevices illustrated in FIG. 3 and FIG. 4 and described above aretypically suitable for low-power applications.

In various embodiments, the present invention realizes high output powerfrom a diode laser is by widening a portion of the laser cavity memberfrom the single lateral mode regime of 1.0-3.0 μm to the multi-lateralmode range 5.0-20 μm. In some cases, laser diodes having cavities at awidth of 50 μm or greater are employed.

The laser stripe length, or cavity length ranges from 100 to 3000 μm andemploys growth and fabrication techniques such as those described inU.S. patent application Ser. No. 12/759,273, filed Apr. 13, 2010, whichis incorporated by reference herein. As an example, laser diodes arefabricated on nonpolar or semipolar gallium containing substrates, wherethe internal electric fields are substantially eliminated or mitigatedrelative to polar c-plane oriented devices. It is to be appreciated thatreduction in internal fields often enables more efficient radiativerecombination. Further, the heavy hole mass is expected to be lighter onnonpolar and semipolar substrates, such that better gain properties fromthe lasers can be achieved.

Optionally, FIG. 4 illustrates an example cross-sectional diagram of agallium and nitrogen based laser diode device. The epitaxial devicestructure is formed on top of the gallium and nitrogen containingsubstrate member 203. The substrate member may be n-type doped with Oand/or Si doping. The epitaxial structures will contain n-side layers205 such as an n-type buffer layer comprised of GaN, AlGaN, AlINGaN, orInGaN and n-type cladding layers comprised of GaN, AlGaN, or AlInGaN.The n-typed layers may have thickness in the range of 0.3 μm to about 3μm or to about 5 μm and may be doped with an n-type carrier such as Sior O to concentrations between 1×10¹⁶ cm⁻³ to 1×10¹⁹ cm⁻³. Overlying then-type layers is the active region and waveguide layers 207. This regioncould contain an n-side waveguide layer or separate confinementheterostructure (SCH) such as InGaN to help with optical guiding of themode. The InGaN layer be comprised of 1 to 15% molar fraction of InNwith a thickness ranging from about 30 nm to about 250 nm and may bedoped with an n-type species such as Si. Overlying the SCH layer is thelight emitting regions which could be comprised of a doubleheterostructure or a quantum well active region. A quantum well activeregion could be comprised of 1 to 10 quantum wells ranging in thicknessfrom 1 nm to 20 nm comprised of InGaN. Barrier layers comprised of GaN,InGaN, or AlGaN separate the quantum well light emitting layers. Thebarriers range in thickness from 1 nm to about 25 nm. Overlying thelight emitting layers are optionally an AlGaN or InAlGaN electronblocking layer with 5% to about 35% AlN and optionally doped with ap-type species such as Mg. Also optional is a p-side waveguide layer orSCH such as InGaN to help with optical guiding of the mode. The InGaNlayer be comprised of 1 to 15% molar fraction of InN with a thicknessranging from 30 nm to about 250 nm and may be doped with an p-typespecies such as Mg. Overlying the active region and optional electronblocking layer and p-side waveguide layers is a p-cladding region and ap++ contact layer. The p-type cladding region is comprised of GaN,AlGaN, AlINGaN, or a combination thereof. The thickness of the p-typecladding layers is in the range of 0.3 μm to about 2 μm and is dopedwith Mg to a concentration of between 1×10¹⁶ cm⁻³ to 1×10¹⁹ cm⁻³. Aridge 211 is formed in the p-cladding region for lateral confinement inthe waveguide using an etching process selected from a dry etching or awet etching process. A dielectric material 213 such as silicon dioxideor silicon nitride or deposited on the surface region of the device andan opening is created on top of the ridge to expose a portion of the p++GaN layer. A p-contact 215 is deposited on the top of the device tocontact the exposed p++ contact region. The p-type contact may becomprised of a metal stack containing a of Au, Pd, Pt, Ni, Ti, or Ag andmay be deposited with electron beam deposition, sputter deposition, orthermal evaporation. A n-contact 201 is formed to the bottom of thesubstrate member. The n-type contact may be comprised of a metal stackcontaining Au, Al, Pd, Pt, Ni, Ti, or Ag and may be deposited withelectron beam deposition, sputter deposition, or thermal evaporation.

In multiple embodiments according to the present invention, the devicelayers comprise a super-luminescent light emitting diode or SLED. In allapplicable embodiments a SLED device can be interchanged with orcombined with laser diode devices according to the methods andarchitectures described in this invention. A SLED is in many wayssimilar to an edge emitting laser diode; however the emitting facet ofthe device is designed so as to have a very low reflectivity. A SLED issimilar to a laser diode as it is based on an electrically drivenjunction that when injected with current becomes optically active andgenerates amplified spontaneous emission (ASE) and gain over a widerange of wavelengths. When the optical output becomes dominated by ASEthere is a knee in the light output versus current (LI) characteristicwherein the unit of light output becomes drastically larger per unit ofinjected current. This knee in the LI curve resembles the threshold of alaser diode, but is much softer. A SLED would have a layer structureengineered to have a light emitting layer or layers clad above and belowwith material of lower optical index such that a laterally guidedoptical mode can be formed. The SLED would also be fabricated withfeatures providing lateral optical confinement. These lateralconfinement features may consist of an etched ridge, with air, vacuum,metal or dielectric material surrounding the ridge and providing a lowoptical-index cladding. The lateral confinement feature may also beprovided by shaping the electrical contacts such that injected currentis confined to a finite region in the device. In such a “gain guided”structure, dispersion in the optical index of the light emitting layerwith injected carrier density provides the optical-index contrast neededto provide lateral confinement of the optical mode.

In an embodiment, the LD or SLED device is characterized by a ridge withnon-uniform width. The ridge is comprised by a first section of uniformwidth and a second section of varying width. The first section has alength between 100 and 500 μm long, though it may be longer. The firstsection has a width of between 1 and 2.5 μm, with a width preferablybetween 1 and 1.5 μm. The second section of the ridge has a first endand a second end. The first end connects with the first section of theridge and has the same width as the first section of the ridge. Thesecond end of the second section of the ridge is wider than the firstsection of the ridge, with a width between 5 and 50 μm and morepreferably with a width between 15 and 35 μm. The second section of theridge waveguide varies in width between its first and second endsmoothly. In some embodiments the second derivative of the ridge widthversus length is zero such that the taper of the ridge is linear. Insome embodiments, the second derivative is chosen to be positive ornegative. In general, the rate of width increase is chosen such that theridge does not expand in width significantly faster than the opticalmode. In specific embodiments, the electrically injected area ispatterned such that only a part of the tapered portion of the waveguideis electrically injected.

In an embodiment, multiple laser dice emitting at different wavelengthsare transferred to the same carrier wafer in close proximity to oneanother; preferably within one millimeter of each other, more preferablywithin about 200 micrometers of each other and most preferably withinabout 50 μm of each other. The laser die wavelengths are chosen to beseparated in wavelength by at least twice the full width at half maximumof their spectra. For example, three dice, emitting at 440 nm, 450 nmand 460 nm, respectively, are transferred to a single carrier chip witha separation between die of less than 50 μm and die widths of less than50 μm such that the total lateral separation, center to center, of thelaser light emitted by the die is less than 200 μm. The closeness of thelaser die allows for their emission to be easily coupled into the sameoptical train or fiber optic waveguide or projected in the far fieldinto overlapping spots. In a sense, the lasers can be operatedeffectively as a single laser light source.

Such a configuration offers an advantage in that each individual laserlight source could be operated independently to convey information usingfor example frequency and phase modulation of an RF signal superimposedon DC offset. The time-averaged proportion of light from the differentsources could be adjusted by adjusting the DC offset of each signal. Ata receiver, the signals from the individual laser sources would bedemultiplexed by use of notch filters over individual photodetectorsthat filter out both the phosphor derived component of the white lightspectra as well as the pump light from all but one of the laser sources.Such a configuration would offer an advantage over an LED based visiblelight communication (VLC) source in that bandwidth would scale easilywith the number of laser emitters. Of course, a similar embodiment withsimilar advantages could be constructed from SLED emitters.

After the laser diode chip fabrication as described above, the laserdiode can be mounted to a submount. In some examples the submount iscomprised of AlN, SiC, BeO, diamond, or other materials such as metals,ceramics, or composites. Alternatively, the submount can be anintermediate submount intended to be mounted to the common supportmember wherein the phosphor material is attached. The submount membermay be characterized by a width, length, and thickness. In an examplewherein the submount is the common support member for the phosphor andthe laser diode chip the submount would have a width and length rangingin dimension from about 0.5 mm to about 5 mm or to about 15 mm and athickness ranging from about 150 μm to about 2 mm. In the examplewherein the submount is an intermediate submount between the laser diodechip and the common support member it could be characterized by widthand length ranging in dimension from about 0.5 mm to about 5 mm and thethickness may range from about 50 μm to about 500 μm. The laser diode isattached to the submount using a bonding process, a soldering process, agluing process, or a combination thereof. In one embodiment the submountis electrically isolating and has metal bond pads deposited on top. Thelaser chip is mounted to at least one of those metal pads. The laserchip can be mounted in a p-side down or a p-side up configuration. Afterbonding the laser chip, wire bonds are formed from the chip to thesubmount such that the final chip on submount (CoS) is completed andready for integration.

A schematic diagram illustrating a CoS based on a conventional laserdiode formed on gallium and nitrogen containing substrate technologyaccording to this present invention is shown in FIG. 5 . The CoS iscomprised of submount material 301 configured to act as an intermediatematerial between a laser diode chip 302 and a final mounting surface.The submount is configured with electrodes 303 and 305 that may beformed with deposited metal layers such as Au. In one example, Ti/Pt/Auis used for the electrodes. Wirebonds 304 are configured to couple theelectrical power from the electrodes 303 and 305 on the submount to thelaser diode chip to generate a laser beam output 306 from the laserdiode. The electrodes 303 and 305 are configured for an electricalconnection to an external power source such as a laser driver, a currentsource, or a voltage source. Wirebonds 304 can be formed on theelectrodes to couple electrical power to the laser diode device andactivate the laser.

In another embodiment, the gallium and nitrogen containing laser diodefabrication includes an epitaxial release step to lift off theepitaxially grown gallium and nitrogen layers and prepare them fortransferring to a carrier wafer which could comprise the submount afterlaser fabrication. The transfer step requires precise placement of theepitaxial layers on the carrier wafer to enable subsequent processing ofthe epitaxial layers into laser diode devices. The attachment process tothe carrier wafer could include a wafer bonding step with a bondinterface comprised of metal-metal, semiconductor-semiconductor,glass-glass, dielectric-dielectric, or a combination thereof.

In this embodiment, gallium and nitrogen containing epitaxial layers aregrown on a bulk gallium and nitrogen containing substrate. The epitaxiallayer stack comprises at least a sacrificial release layer and the laserdiode device layers overlying the release layers. Following the growthof the epitaxial layers on the bulk gallium and nitrogen containingsubstrate, the semiconductor device layers are separated from thesubstrate by a selective wet etching process such as a PEC etchconfigured to selectively remove the sacrificial layers and enablerelease of the device layers to a carrier wafer. In one embodiment, abonding material is deposited on the surface overlying the semiconductordevice layers. A bonding material is also deposited either as a blanketcoating or patterned on the carrier wafer. Standard lithographicprocesses are used to selectively mask the semiconductor device layers.The wafer is then subjected to an etch process such as dry etch or wetetch processes to define via structures that expose the sacrificiallayers on the sidewall of the mesa structure. As used herein, the termmesa region or mesa is used to describe the patterned epitaxial materialon the gallium and nitrogen containing substrate and prepared fortransferring to the carrier wafer. The mesa region can be any shape orform including a rectangular shape, a square shape, a triangular shape,a circular shape, an elliptical shape, a polyhedron shape, or othershape. The term mesa shall not limit the scope of the present invention.

Following the definition of the mesa, a selective etch process isperformed to fully or partially remove the sacrificial layers whileleaving the semiconductor device layers intact. The resulting structurecomprises undercut mesas comprised of epitaxial device layers. Theundercut mesas correspond to dice from which semiconductor devices willbe formed on. In some embodiments a protective passivation layer can beemployed on the sidewall of the mesa regions to prevent the devicelayers from being exposed to the selective etch when the etchselectivity is not perfect. In other embodiments a protectivepassivation is not needed because the device layers are not sensitive tothe selective etch or measures are taken to prevent etching of sensitivelayers such as shorting the anode and cathode. The undercut mesascorresponding to device dice are then transferred to the carrier waferusing a bonding technique wherein the bonding material overlying thesemiconductor device layers is joined with the bonding material on thecarrier wafer. The resulting structure is a carrier wafer comprisinggallium and nitrogen containing epitaxial device layers overlying thebonding region.

In a preferred embodiment PEC etching is deployed as the selective etchto remove the sacrificial layers. PEC is a photo-assisted wet etchtechnique that can be used to etch GaN and its alloys. The processinvolves an above-band-gap excitation source and an electrochemical cellformed by the semiconductor and the electrolyte solution. In this case,the exposed (Al,In,Ga)N material surface acts as the anode, while ametal pad deposited on the semiconductor acts as the cathode. Theabove-band-gap light source generates electron-hole pairs in thesemiconductor. Electrons are extracted from the semiconductor via thecathode while holes diffuse to the surface of material to form an oxide.Since the diffusion of holes to the surface requires the band bending atthe surface to favor a collection of holes, PEC etching typically worksonly for n-type material although some methods have been developed foretching p-type material. The oxide is then dissolved by the electrolyteresulting in wet etching of the semiconductor. Different types ofelectrolyte including HCl, KOH, and HNO₃ have been shown to be effectivein PEC etching of GaN and its alloys. The etch selectivity and etch ratecan be optimized by selecting a favorable electrolyte. It is alsopossible to generate an external bias between the semiconductor and thecathode to assist with the PEC etching process.

In a preferred embodiment, a semiconductor device epitaxy material withthe underlying sacrificial region is fabricated into a dense array ofmesas on the gallium and nitrogen containing bulk substrate with theoverlying semiconductor device layers. The mesas are formed using apatterning and a wet or dry etching process wherein the patterningcomprises a lithography step to define the size and pitch of the mesaregions. Dry etching techniques such as reactive ion etching,inductively coupled plasma etching, or chemical assisted ion beametching are candidate methods. Alternatively, a wet etch can be used.The etch is configured to terminate at or below a sacrificial regionbelow the device layers. This is followed by a selective etch processsuch as PEC to fully or partially etch the exposed sacrificial regionsuch that the mesas are undercut. This undercut mesa pattern pitch willbe referred to as the ‘first pitch’. The first pitch is often a designwidth that is suitable for fabricating each of the epitaxial regions onthe substrate, while not large enough for the desired completedsemiconductor device design, which often desire larger non-activeregions or regions for contacts and the like. For example, these mesaswould have a first pitch ranging from about 5 μm to about 500 μm or toabout 5000 μm. Each of these mesas is a ‘die’.

In a preferred embodiment, these dice are transferred to a carrier waferat a second pitch using a selective bonding process such that the secondpitch on the carrier wafer is greater than the first pitch on thegallium and nitrogen containing substrate. In this embodiment the diceare on an expanded pitch for so called “die expansion”. In an example,the second pitch is configured with the dice to allow each die with aportion of the carrier wafer to be a semiconductor device, includingcontacts and other components. For example, the second pitch would beabout 50 μm to about 1000 μm or to about 5000 μm, but could be as largeat about 3-10 mm or greater in the case where a large semiconductordevice chip is required for the application. The larger second pitchcould enable easier mechanical handling without the expense of thecostly gallium and nitrogen containing substrate and epitaxial material,allow the real estate for additional features to be added to thesemiconductor device chip such as bond pads that do not require thecostly gallium and nitrogen containing substrate and epitaxial material,and/or allow a smaller gallium and nitrogen containing epitaxial wafercontaining epitaxial layers to populate a much larger carrier wafer forsubsequent processing for reduced processing cost. For example, a 4 to 1die expansion ratio would reduce the density of the gallium and nitrogencontaining material by a factor of 4, and hence populate an area on thecarrier wafer 4 times larger than the gallium and nitrogen containingsubstrate. This would be equivalent to turning a 2″ gallium and nitrogensubstrate into a 4″ carrier wafer. In particular, the present inventionincreases utilization of substrate wafers and epitaxy material through aselective area bonding process to transfer individual die of epitaxymaterial to a carrier wafer in such a way that the die pitch isincreased on the carrier wafer relative to the original epitaxy wafer.The arrangement of epitaxy material allows device components which donot require the presence of the expensive gallium and nitrogencontaining substrate and overlying epitaxy material often fabricated ona gallium and nitrogen containing substrate to be fabricated on thelower cost carrier wafer, allowing for more efficient utilization of thegallium and nitrogen containing substrate and overlying epitaxymaterial.

FIG. 6 is a schematic representation of the die expansion process withselective area bonding according to the present invention. A devicewafer is prepared for bonding in accordance with an embodiment of thisinvention. The device wafer consists of a substrate 606, buffer layers603, a fully removed sacrificial layer 609, device layers 602, bondingmedia 601, cathode metal 605, and an anchor material 604. Thesacrificial layer 609 is removed in the PEC etch with the anchormaterial 604 is retained. The mesa regions formed in the gallium andnitrogen containing epitaxial wafer form dice of epitaxial material andrelease layers defined through processing. Individual epitaxial materialdie are formed at first pitch. A carrier wafer is prepared consisting ofthe carrier wafer substrate 607 and bond pads 608 at second pitch. Thesubstrate 606 is aligned to the carrier wafer 607 such that a subset ofthe mesa on the gallium and nitrogen containing substrate 606 with afirst pitch aligns with a subset of bond pads 608 on the carrier wafer607 at a second pitch. Since the first pitch is greater than the secondpitch and the mesas will comprise device die, the basis for dieexpansion is established. The bonding process is carried out and uponseparation of the substrate from the carrier wafer 607 the subset ofmesas on the substrate 606 are selectively transferred to the carrierwafer 607. The process is then repeated with a second set of mesas andbond pads 608 on the carrier wafer 607 until the carrier wafer 607 ispopulated fully by epitaxial mesas. The gallium and nitrogen containingepitaxy substrate 201 can now optionally be prepared for reuse.

In the example depicted in FIG. 6 , one quarter of the epitaxial dice onthe epitaxy wafer 606 are transferred in this first selective bond step,leaving three quarters on the epitaxy wafer 606. The selective areabonding step is then repeated to transfer the second quarter, thirdquarter, and fourth quarter of the epitaxial die to the patternedcarrier wafer 607. This selective area bond may be repeated any numberof times and is not limited to the four steps depicted in FIG. 6 . Theresult is an array of epitaxial die on the carrier wafer 607 with awider die pitch than the original die pitch on the epitaxy wafer 606.The die pitch on the epitaxial wafer 606 will be referred to as pitch 1,and the die pitch on the carrier wafer 607 will be referred to as pitch2, where pitch 2 is greater than pitch 1.

In one embodiment the bonding between the carrier wafer and the galliumand nitrogen containing substrate with epitaxial layers is performedbetween bonding layers that have been applied to the carrier and thegallium and nitrogen containing substrate with epitaxial layers. Thebonding layers can be a variety of bonding pairs including metal-metal,oxide-oxide, soldering alloys, photoresists, polymers, wax, etc. Onlyepitaxial dice which are in contact with a bond bad 608 on the carrierwafer 607 will bond. Sub-micron alignment tolerances are possible oncommercial die bonders. The epitaxy wafer 606 is then pulled away,breaking the epitaxy material at a weakened epitaxial release layer 609such that the desired epitaxial layers remain on the carrier wafer 607.Herein, a ‘selective area bonding step’ is defined as a single iterationof this process.

In one embodiment, the carrier wafer 607 is patterned in such a way thatonly selected mesas come in contact with the metallic bond pads 608 onthe carrier wafer 607. When the epitaxy substrate 606 is pulled away thebonded mesas break off at the weakened sacrificial region, while theun-bonded mesas remain attached to the epitaxy substrate 606. Thisselective area bonding process can then be repeated to transfer theremaining mesas in the desired configuration. This process can berepeated through any number of iterations and is not limited to the twoiterations depicted in FIG. 6 . The carrier wafer can be of any size,including but not limited to about 2 inch, 3 inch, 4 inch, 6 inch, 8inch, and 12 inch. After all desired mesas have been transferred, asecond bandgap selective PEC etching can be optionally used to removeany remaining sacrificial region material to yield smooth surfaces. Atthis point standard semiconductor device processes can be carried out onthe carrier wafer. Another embodiment of the invention incorporates thefabrication of device components on the dense epitaxy wafers before theselective area bonding steps.

In an example, the present invention provides a method for increasingthe number of gallium and nitrogen containing semiconductor deviceswhich can be fabricated from a given epitaxial surface area; where thegallium and nitrogen containing epitaxial layers overlay gallium andnitrogen containing substrates. The gallium and nitrogen containingepitaxial material is patterned into die with a first die pitch; the diefrom the gallium and nitrogen containing epitaxial material with a firstpitch is transferred to a carrier wafer to form a second die pitch onthe carrier wafer; the second die pitch is larger than the first diepitch.

In an example, each epitaxial device die is an etched mesa with a pitchof between about 1 μm and about 100 μm wide or between about 100 μm andabout 500 μm wide or between about 500 μm and about 3000 μm wide andbetween about 100 and about 3000 μm long. In an example, the second diepitch on the carrier wafer is between about 100 μm and about 200 μm orbetween about 200 μm and about 1000 μm or between about 1000 μm andabout 3000 μm. In an example, the second die pitch on the carrier waferis between about 2 times and about 50 times larger than the die pitch onthe epitaxy wafer. In an example, semiconductor LED devices, laserdevices, or electronic devices are fabricated on the carrier wafer afterepitaxial transfer. In an example, the semiconductor devices containGaN, AlN, InN, InGaN, AlGaN, InAlN, and/or InAlGaN. In an example, thegallium and nitrogen containing material are grown on a polar, nonpolar,or semipolar plane. In an example, one or multiple semiconductor devicesare fabricated on each die of epitaxial material. In an example, devicecomponents which do not require epitaxy material are placed in the spacebetween epitaxy die.

In one embodiment, device dice are transferred to a carrier wafer suchthat the distance between die is expanded in both the transverse as wellas lateral directions. This can be achieved by spacing bond pads on thecarrier wafer with larger pitches than the spacing of device die on thesubstrate.

In another embodiment of the invention device dice from a plurality ofepitaxial wafers are transferred to the carrier wafer such that eachdesign width on the carrier wafer contains dice from a plurality ofepitaxial wafers. When transferring dice at close spacing from multipleepitaxial wafers, it is important for the un-transferred dice on theepitaxial wafer to not inadvertently contact and bond to die alreadytransferred to the carrier wafer. To achieve this, epitaxial dice from afirst epitaxial wafer are transferred to a carrier wafer using themethods described above. A second set of bond pads are then deposited onthe carrier wafer and are made with a thickness such that the bondingsurface of the second pads is higher than the top surface of the firstset of transferred die. This is done to provide adequate clearance forbonding of the dice from the second epitaxial wafer. A second epitaxialwafer transfers a second set of dice to the carrier wafer. Finally, thesemiconductor devices are fabricated, and passivation layers aredeposited followed by electrical contact layers that allow each die tobe individually driven. The dice transferred from the first and secondsubstrates are spaced at a pitch which is smaller than the second pitchof the carrier wafer. This process can be extended to transfer of dicefrom any number of epitaxial substrates, and to transfer of any numberof devices per dice from each epitaxial substrate.

A schematic diagram illustrating a CoS based on lifted off andtransferred epitaxial gallium and nitrogen containing layers accordingto this present invention is shown in FIG. 7 . The CoS is comprised ofsubmount material 901 configured from the carrier wafer with thetransferred epitaxial material with a laser diode configured within theepitaxy 902. Electrodes 903 and 904 are electrically coupled to then-side and the p-side of the laser diode device and configured totransmit power from an external source to the laser diode to generate alaser beam output 905 from the laser diode. The electrodes areconfigured for an electrical connection to an external power source suchas a laser driver, a current source, or a voltage source. Wirebonds canbe formed on the electrodes to couple the power to the laser diodedevice. This integrated CoS device with transferred epitaxial materialoffers advantages over the conventional configuration such as size,cost, and performance due to the low thermal impedance.

Further process and device description for this embodiment describinglaser diodes formed in gallium and nitrogen containing epitaxial layersthat have been transferred from the native gallium and nitrogencontaining substrates are described in U.S. patent application Ser. No.14/312,427 and U.S. Patent Publication No. 2015/0140710, which areincorporated by reference herein. As an example, this technology of GaNtransfer can enable lower cost, higher performance, and a more highlymanufacturable process flow.

Phosphor selection is a key consideration within the laser basedintegrated white light source. The phosphor must be able to withstandthe extreme optical intensity and associated heating induced by thelaser excitation spot without severe degradation. Importantcharacteristics to consider for phosphor selection include:

-   -   A high conversion efficiency of optical excitation power to        white light lumens. In the example of a blue laser diode        exciting a yellow phosphor, a conversion efficiency of over 150        lumens per optical watt, or over 200 lumens per optical watt, or        over 300 lumens per optical watt is desired.    -   A high optical damage threshold capable of withstanding 1-20 W        of laser power in a spot comprising a diameter of 1 mm, 500 μm,        200 μm, 100 μm, or even 50 μm.    -   High thermal damage threshold capable of withstanding        temperatures of over 150° C., over 200° C., or over 300° C.        without decomposition.    -   A low thermal quenching characteristic such that the phosphor        remains efficient as it reaches temperatures of over 150° C.,        200° C., or 250° C.    -   A high thermal conductivity to dissipate the heat and regulate        the temperature. Thermal conductivities of greater than 3 W/m-K,        greater than 5 W/m-K, greater than 10 W/m-K, and even greater        than 15 W/m-K are desirable.    -   A proper phosphor emission color for the application.    -   A suitable porosity characteristic that leads to the desired        scattering of the coherent excitation without unacceptable        reduction in thermal conductivity or optical efficiency.    -   A proper form factor for the application. Such form factors        include, but are not limited to blocks, plates, disks, spheres,        cylinders, rods, or a similar geometrical element. Proper choice        will be dependent on whether phosphor is operated in        transmissive or reflective mode and on the absorption length of        the excitation light in the phosphor.    -   A surface condition optimized for the application. In an        example, the phosphor surfaces can be intentionally roughened        for improved light extraction.

In a preferred embodiment, a blue laser diode operating in the 420 nm to480 nm wavelength range would be combined with a phosphor materialproviding a yellowish emission in the 560 nm to 580 nm range such thatwhen mixed with the blue emission of the laser diode a white light isproduced. For example, to meet a white color point on the black bodyline the energy of the combined spectrum may be comprised of about 30%from the blue laser emission and about 70% from the yellow phosphoremission. In other embodiments phosphors with red, green, yellow, andeven blue emission can be used in combination with the laser diodeexcitation sources in the violet, ultra-violet, or blue wavelength rangeto produce a white light with color mixing. Although such white lightsystems may be more complicated due to the use of more than one phosphormember, advantages such as improved color rendering could be achieved.

In an example, the light emitted from the laser diodes is partiallyconverted by the phosphor element. In an example, the partiallyconverted light emitted generated in the phosphor element results in acolor point, which is white in appearance. In an example, the colorpoint of the white light is located on the Planckian blackbody locus ofpoints. In an example, the color point of the white light is locatedwithin du′v′ of less than 0.010 of the Planckian blackbody locus ofpoints. In an example, the color point of the white light is preferablylocated within du′v′ of less than 0.03 of the Planckian blackbody locusof points.

The phosphor material can be operated in a transmissive mode, areflective mode, or a combination of a transmissive mode and reflectivemode, or other modes. The phosphor material is characterized by aconversion efficiency, a resistance to thermal damage, a resistance tooptical damage, a thermal quenching characteristic, a porosity toscatter excitation light, and a thermal conductivity. In a preferredembodiment the phosphor material is comprised of a yellow emitting YAGmaterial doped with Ce with a conversion efficiency of greater than 100lumens per optical watt, greater than 200 lumens per optical watt, orgreater than 300 lumens per optical watt, and can be a polycrystallineceramic material or a single crystal material.

In some embodiments of the present invention, the environment of thephosphor can be independently tailored to result in high efficiency withlittle or no added cost. Phosphor optimization for laser diodeexcitation can include high transparency, scattering or non-scatteringcharacteristics, and use of ceramic phosphor plates. Decreasedtemperature sensitivity can be determined by doping levels. A reflectorcan be added to the backside of a ceramic phosphor, reducing loss. Thephosphor can be shaped to increase in-coupling, increase out-coupling,and/or reduce back reflections. Surface roughening is a well-known meansto increase extraction of light from a solid material. Coatings,mirrors, or filters can be added to the phosphors to reduce the amountof light exiting the non-primary emission surfaces, to promote moreefficient light exit through the primary emission surface, and topromote more efficient in-coupling of the laser excitation light. Ofcourse, there can be additional variations, modifications, andalternatives.

In some embodiments, certain types of phosphors will be best suited inthis demanding application with a laser excitation source. As anexample, ceramic yttrium aluminum garnets (YAG) doped with Ce³⁺ ions, orYAG based phosphors can be ideal candidates. They are doped with speciessuch as Ce to achieve the proper emission color and are often comprisedof a porosity characteristic to scatter the excitation source light, andnicely break up the coherence in laser excitation. As a result of itscubic crystal structure the YAG:Ce can be prepared as a highlytransparent single crystal as well as a polycrystalline bulk material.The degree of transparency and the luminescence are depending on thestoichiometric composition, the content of dopant, and entire processingand sintering route. The transparency and degree of scattering centerscan be optimized for a homogenous mixture of blue and yellow light. TheYAG:Ce can be configured to emit a green emission. In some embodimentsthe YAG can be doped with Eu to emit a red emission.

In a preferred embodiment according to this invention, the white lightsource is configured with a ceramic polycrystalline YAG:Ce phosphorscomprising an optical conversion efficiency of greater than 100 lumensper optical excitation watt, of greater than 200 lumens per opticalexcitation watt, or even greater than 300 lumens per optical excitationwatt. Additionally, the ceramic YAG:Ce phosphors is characterized by atemperature quenching characteristics above 150° C., above 200° C., orabove 250° C. and a high thermal conductivity of 5-10 W/m-K toeffectively dissipate heat to a heat sink member and keep the phosphorat an operable temperature.

In another preferred embodiment according to this invention, the whitelight source is configured with a single crystal phosphor (SCP) such asYAG:Ce. In one example the Ce:Y₃Al₅O₁₂ SCP can be grown by theCzochralski technique. In this embodiment according the presentinvention the SCP based on YAG:Ce is characterized by an opticalconversion efficiency of greater than 100 lumens per optical excitationwatt, of greater than 200 lumens per optical excitation watt, or evengreater than 300 lumens per optical excitation watt. Additionally, thesingle crystal YAG:Ce phosphors is characterized by a temperaturequenching characteristics above 150° C., above 200° C., or above 300° C.and a high thermal conductivity of 8-20 W/m-K to effectively dissipateheat to a heat sink member and keep the phosphor at an operabletemperature. In addition to the high thermal conductivity, high thermalquenching threshold, and high conversion efficiency, the ability toshape the phosphors into tiny forms that can act as ideal “point”sources when excited with a laser is an attractive feature.

In some embodiments the YAG:Ce can be configured to emit a yellowemission. In alternative or the same embodiments a YAG:Ce can beconfigured to emit a green emission. In yet alternative or the sameembodiments the YAG can be doped with Eu to emit a red emission. In someembodiments a LuAG is configured for emission. In alternativeembodiments, silicon nitrides or aluminum-oxi-nitrides can be used asthe crystal host materials for red, green, yellow, or blue emissions.

In an alternative embodiment, a powdered single crystal or ceramicphosphor such as a yellow phosphor or green phosphor is included. Thepowdered phosphor can be dispensed on a transparent member for atransmissive mode operation or on a solid member with a reflective layeron the back surface of the phosphor or between the phosphor and thesolid member to operate in a reflective mode. The phosphor powder may beheld together in a solid structure using a binder material wherein thebinder material is preferable in inorganic material with a high opticaldamage threshold and a favorable thermal conductivity. The phosphorpower may be comprised of a colored phosphor and configured to emit awhite light when excited by and combined with the blue laser beam orexcited by a violet laser beam. The powdered phosphors could becomprised of YAG, LuAG, or other types of phosphors.

In one embodiment of the present invention the phosphor materialcontains a yttrium aluminum garnet host material and a rare earth dopingelement, and others. In an example, the wavelength conversion element isa phosphor which contains a rare earth doping element, selected from aof Ce, Nd, Er, Yb, Ho, Tm, Dy and Sm, combinations thereof, and thelike. In an example, the phosphor material is a high-density phosphorelement. In an example, the high-density phosphor element has a densitygreater than 90% of pure host crystal. Cerium (III)-doped YAG (YAG:Ce³⁺,or Y₃Al₅O₁₂:Ce³⁺) can be used wherein the phosphor absorbs the lightfrom the blue laser diode and emits in a broad range from greenish toreddish, with most of output in yellow. This yellow emission combinedwith the remaining blue emission gives the “white” light, which can beadjusted to color temperature as warm (yellowish) or cold (bluish)white. The yellow emission of the Ce³⁺:YAG can be tuned by substitutingthe cerium with other rare earth elements such as terbium and gadoliniumand can even be further adjusted by substituting some or all of thealuminum in the YAG with gallium.

In alternative examples, various phosphors can be applied to thisinvention, which include, but are not limited to organic dyes,conjugated polymers, semiconductors such as AlInGaP or InGaN, yttriumaluminum garnets (YAGs) doped with Ce³⁺ ions(Y_(1-a)Gd_(a))₃(Al_(1-b)Ga_(b))₅O₁₂:Ce³⁺, SrGa₂S₄:Eu²⁺, SrS:Eu²⁺,terbium aluminum based garnets (TAGs) (Tb₃Al₅O₅), colloidal quantum dotthin films containing CdTe, ZnS, ZnSe, ZnTe, CdSe, or CdTe.

In further alternative examples, some rare-earth doped SiAlONs can serveas phosphors. Europium(II)-doped β-SiAlON absorbs in ultraviolet andvisible light spectrum and emits intense broadband visible emission. Itsluminance and color does not change significantly with temperature, dueto the temperature-stable crystal structure. In an alternative example,green and yellow SiAlON phosphor and a red CaAlSiN₃-based (CASN)phosphor may be used.

In yet a further example, white light sources can be made by combiningnear ultraviolet emitting laser diodes with a mixture of high efficiencyeuropium based red and blue emitting phosphors plus green emittingcopper and aluminum doped zinc sulfide (ZnS:Cu,Al).

In an example, a phosphor or phosphor blend can be selected from a of(Y, Gd, Tb, Sc, Lu, La)₃(Al, Ga, In)₅O₁₂:Ce³⁺, SrGa₂S₄:Eu²⁺, SrS:Eu²⁺,and colloidal quantum dot thin films comprising CdTe, ZnS, ZnSe, ZnTe,CdSe, or CdTe. In an example, a phosphor is capable of emittingsubstantially red light, wherein the phosphor is selected from a of thegroup consisting of (Gd,Y,Lu,La)₂O₃:Eu³⁺, Bi³⁺; (Gd,Y,Lu,La)₂O₂S:Eu³⁺,Bi³⁺; (Gd,Y,Lu,La)VO₄:Eu³⁺, Bi³⁺; Y₂(O,S)₃:Eu³⁺;Ca_(1-x)Mo_(1-y)Si_(y)O₄: where 0.05<x<0.5, 0<y<0.1;(Li,Na,K)₅Eu(W,Mo)O₄; (Ca,Sr)S:Eu²⁺; SrY₂S₄:Eu²⁺; CaLa₂S₄:Ce³⁺;(Ca,Sr)S:Eu²⁺; 3.5MgO×0.5MgF₂×GeO₂:Mn⁴⁺ (MFG);(Ba,Sr,Ca)Mg_(x)P₂O₇:Eu²⁺, Mn²⁺; (Y,Lu)₂WO₆:Eu³⁺, Mo⁶⁺;(Ba,Sr,Ca)₃Mg_(x)Si₂O₈:Eu²⁺, Mn²⁺, wherein 1<x<2;(RE_(1-y)Ce_(y))Mg_(2-x)Li_(x)Si_(3-x)P_(x)O₁₂, where RE is at least oneof Sc, Lu, Gd, Y, and Tb, 0.0001<x<0.1 and 0.001<y<0.1; (Y, Gd, Lu,La)_(2-x)Eu_(x)W_(1-y)Mo_(y)O₆, where 0.5<x<1.0, 0.01<y<1.0;(SrCa)_(1-x)Eu_(x)Si₅N₈, where 0.01<x<0.3; SrZnO₂:Sm⁺³; M_(m)O_(n)X,wherein M is selected from the group of Sc, Y, a lanthanide, an alkaliearth metal and mixtures thereof; X is a halogen; 1<m<3; and 1<n<4, andwherein the lanthanide doping level can range from 0.1 to 40% spectralweight; and Eu³⁺ activated phosphate or borate phosphors; and mixturesthereof. Further details of other phosphor species and relatedtechniques can be found in U.S. Pat. No. 8,956,894, in the name ofRaring et al. issued Feb. 17, 2015, and titled “White light devicesusing non-polar or semipolar gallium containing materials andphosphors”, which is commonly owned, and hereby incorporated byreference herein.

In some embodiments of the present invention, ceramic phosphor materialsare embedded in a binder material such as silicone. This configurationis typically less desirable because the binder materials often have poorthermal conductivity, and thus get very hot wherein the rapidly degradeand even burn. Such “embedded” phosphors are often used in dynamicphosphor applications such as color wheels where the spinning wheelcools the phosphor and spreads the excitation spot around the phosphorin a radial pattern.

Sufficient heat dissipation from the phosphor is a critical designconsideration for the integrated white light source based on laser diodeexcitation. Specifically, the optically pumped phosphor system hassources of loss in the phosphor that result is thermal energy and hencemust be dissipated to a heat-sink for optimal performance. The twoprimary sources of loss are the Stokes loss which is a result ofconverting photons of higher energy to photons of lower energy such thatdifference in energy is a resulting loss of the system and is dissipatedin the form of heat. Additionally, the quantum efficiency or quantumyield measuring the fraction of absorbed photons that are successfullyre-emitted is not unity such that there is heat generation from otherinternal absorption processes related to the non-converted photons.Depending on the excitation wavelength and the converted wavelength, theStokes loss can lead to greater than 10%, greater than 20%, and greaterthan 30%, and greater loss of the incident optical power to result inthermal power that must be dissipated. The quantum losses can lead to anadditional 10%, greater than 20%, and greater than 30%, and greater ofthe incident optical power to result in thermal power that must bedissipated. With laser beam powers in the 1 W to 100 W range focused tospot sizes of less than 1 mm in diameter, less than 500 μm in diameter,or even less than 100 μm in diameter, power densities of over 1 W/mm²,100 W/mm², or even over 2,500 W/mm² can be generated. As an example,assuming that the spectrum is comprised of 30% of the blue pump lightand 70% of the converted yellow light and a best case scenario on Stokesand quantum losses, we can compute the dissipated power density in theform of heat for a 10% total loss in the phosphor at 0.1 W/mm², 10W/mm², or even over 250 W/mm². Thus, even for this best-case scenarioexample, this is a tremendous amount of heat to dissipate. This heatgenerated within the phosphor under the high intensity laser excitationcan limit the phosphor conversion performance, color quality, andlifetime.

For optimal phosphor performance and lifetime, not only should thephosphor material itself have a high thermal conductivity, but it shouldalso be attached to the submount or common support member with a highthermal conductivity joint to transmit the heat away from the phosphorand to a heat-sink. In this invention, the phosphor is attached to aremote submount member that is packaged in a separate assembly. In someembodiments, a heatsink can be used to support the phosphor for releaseheat generated during wavelength conversion. Ideally the phosphor bondinterface will have a substantially large area with a flat surface onboth the phosphor side and the support member sides of the interface.

In the present invention, the laser diode output beam must be configuredto be incident on the phosphor material to excite the phosphor. In someembodiments the laser beam may be directly incident on the phosphor andin other embodiments the laser beam may interact with an optic,reflector, waveguide, or other object to manipulate the beam prior toincidence on the phosphor. Examples of such optics include, but are notlimited to ball lenses, aspheric collimator, aspheric lens, fast or slowaxis collimators, dichroic mirrors, turning mirrors, optical isolators,but could be others.

In some embodiments, the apparatus typically has a free space with anon-guided laser beam characteristic transmitting the emission of thelaser beam from the laser device to the phosphor material. The laserbeam spectral width, wavelength, size, shape, intensity, andpolarization are configured to excite the phosphor material. The beamcan be configured by positioning it at the precise distance from thephosphor to exploit the beam divergence properties of the laser diodeand achieve the desired spot size. In one embodiment, the incident anglefrom the laser to the phosphor is optimized to achieve a desired beamshape on the phosphor. For example, due to the asymmetry of the laseraperture and the different divergent angles on the fast and slow axis ofthe beam the spot on the phosphor produced from a laser that isconfigured normal to the phosphor would be elliptical in shape,typically with the fast axis diameter being larger than the slow axisdiameter. To compensate this, the laser beam incident angle on thephosphor can be optimized to stretch the beam in the slow axis directionsuch that the beam is more circular on phosphor. In other embodimentsfree space optics such as collimating lenses can be used to shape thebeam prior to incidence on the phosphor. The beam can be characterizedby a polarization purity of greater than 50% and less than 100%. As usedherein, the term “polarization purity” means greater than 50% of theemitted electromagnetic radiation is in a substantially similarpolarization state such as the transverse electric (TE) or transversemagnetic (TM) polarization states, but can have other meaningsconsistent with ordinary meaning.

The white light apparatus also has an electrical input interfaceconfigured to couple electrical input power to the laser diode device togenerate the laser beam and excite the phosphor material. In an example,the laser beam incident on the phosphor has a power of less than 0.1 W,greater than 0.1 W, greater than 0.5 W, greater than 1 W, greater than 5W, greater than 10 W, or greater than 20 W. The white light sourceconfigured to produce greater than 1 lumen, 10 lumens, 100 lumens, 1000lumens, 10,000 lumens, or greater of white light output.

The support member is configured to transport thermal energy from the atleast one laser diode device and the phosphor material to a heat sink.The support member is configured to provide thermal impedance of lessthan 10 degrees Celsius per watt, less than 5 degrees Celsius per watt,or less than 3 degrees Celsius per watt of dissipated powercharacterizing a thermal path from the laser device to a heat sink. Thesupport member is comprised of a thermally conductive material such ascopper with a thermal conductivity of about 400 W/(m-K), aluminum with athermal conductivity of about 200 W/(mK), 4H—SiC with a thermalconductivity of about 370 W/(m-K), 6H—SiC with a thermal conductivity ofabout 490 W/(m-K), AlN with a thermal conductivity of about 230 W/(m-K),a synthetic diamond with a thermal conductivity of about >1000 W/(m-K),sapphire, or other metals, ceramics, or semiconductors. The supportmember may be formed from a growth process such as SiC, AlN, orsynthetic diamond, and then mechanically shaped by machining, cutting,trimming, or molding. Alternatively, the support member may be formedfrom a metal such as copper, copper tungsten, aluminum, or other bymachining, cutting, trimming, or molding.

Currently, solid state lighting is dominated by systems utilizing blueor violet emitting light emitting diodes (LEDs) to excite phosphorswhich emit a broader spectrum. The combined spectrum of the so-calledpump LEDs and the phosphors can be optimized to yield white lightspectra with controllable color point and good color rendering index.Peak wall plug efficiencies for state of the art LEDs are quite high,above 70%, such that LED based white light bulbs are now the leadinglighting technology for luminous efficacy. As laser light sources,especially high-power blue laser diodes made from gallium and nitrogencontaining material based novel manufacture processes, have shown manyadvantageous functions on quantum efficiency, power density, modulationrate, surface brightness over conventional LEDs. This opens up theopportunity to use lighting fixtures, lighting systems, displays,projectors and the like based on solid-state light sources as a means oftransmitting information with high bandwidth using visible light. Italso enables utilizing the modulated laser signal or direct laser lightspot manipulation to measure and or interact with the surroundingenvironment, transmit data to other electronic systems and responddynamically to inputs from various sensors. Such applications are hereinreferred to as “smart lighting” applications.

In some embodiments, the present invention provides novel uses andconfigurations of gallium and nitrogen containing laser diodes incommunication systems such as visible light communication systems. Morespecifically the present invention provides communication systemsrelated to smart lighting applications with gallium-and-nitrogen-basedlasers light sources coupled to one or more sensors with a feedback loopor control circuitry to trigger the light source to react with one ormore predetermined responses and combinations of smart lighting andvisible light communication. In these systems, light is generated usinglaser devices which are powered by one or more laser drivers. In someembodiments, individual laser devices are used and optical elements areprovided to combine the red, green and blue spectra into a white lightspectrum. In other embodiments, blue or violet laser light is providedby a laser source and is partially or fully converted by a wavelengthconverting element into a broader spectrum of longer wavelength lightsuch that a white light spectrum is produced.

The blue or violet laser devices illuminate a wavelength convertingelement which absorbs part of the pump light and reemits a broaderspectrum of longer wavelength light. The light absorbed by thewavelength converting element is referred to as the “pump” light. Thelight engine is configured such that some portion of both light from thewavelength converting element and the unconverted pump light are emittedfrom the light-engine. When the non-converted, blue pump light and thelonger wavelength light emitted by the wavelength converting element arecombined, they may form a white light spectrum. In an example, thepartially converted light emitted generated in the wavelength conversionelement results in a color point, which is white in appearance. In anexample, the color point of the white light is located on the Planckianblackbody locus of points. In an example, the color point of the whitelight is located within du′v′ of less than 0.010 of the Planckianblackbody locus of points. In an example, the color point of the whitelight is preferably located within du′v′ of less than 0.03 of thePlanckian blackbody locus of points.

In an example, the wavelength conversion element is a phosphor whichcontains garnet host material and a doping element. In an example, thewavelength conversion element is a phosphor, which contains an yttriumaluminum garnet host material and a rare earth doping element, andothers. In an example, the wavelength conversion element is a phosphorwhich contains a rare earth doping element, selected from one or more ofNd, Cr, Er, Yb, Nd, Ho, Tm Cr, Dy, Sm, Tb and Ce, combinations thereof,and the like. In an example, the wavelength conversion element is aphosphor which contains oxy-nitrides containing one or more of Ca, Sr,Ba, Si, Al with or without rare-earth doping. In an example, thewavelength conversion element is a phosphor which contains alkalineearth silicates such as M₂SiO₄:Eu²⁺ (where M is one or more of Ba²⁺,Sr²⁺ and Ca²⁺). In an example, the wavelength conversion element is aphosphor which contains Sr₂LaAlO₅:Ce³⁺, Sr₃SiO₅:Ce³⁺ or Mn⁴⁺-dopedfluoride phosphors. In an example, the wavelength conversion element isa high-density phosphor element. In an example, the wavelengthconversion element is a high-density phosphor element with densitygreater than 90% of pure host crystal. In an example, the wavelengthconverting material is a powder. In an example, the wavelengthconverting material is a powder suspended or embedded in a glass,ceramic or polymer matrix. In an example, the wavelength convertingmaterial is a single crystalline member. In an example, the wavelengthconverting material is a powder sintered to density of greater than 75%of the fully dense material. In an example, the wavelength convertingmaterial is a sintered mix of powders with varying composition and/orindex of refraction. In an example, the wavelength converting element isone or more species of phosphor powder or granules suspended in a glassyor polymer matrix. In an example, the wavelength conversion element is asemiconductor. In an example, the wavelength conversion element containsquantum dots of semiconducting material. In an example, the wavelengthconversion element is comprised by semiconducting powder or granules.

For laser diodes the phosphor may be remote from the laser die, enablingthe phosphor to be well heat sunk, enabling high input power density.This is an advantageous configuration relative to LEDs, where thephosphor is typically in contact with the LED die. While remote-phosphorLEDs do exist, because of the large area and wide emission angle ofLEDs, remote phosphors for LEDs have the disadvantage of requiringsignificantly larger volumes of phosphor to efficiently absorb andconvert all of the LED light, resulting in white light emitters withlarge emitting areas and low luminance.

For LEDs, the phosphor emits back into the LED die where the light fromthe phosphor can be lost due to absorption. For laser diode modules, theenvironment of the phosphor can be independently tailored to result inhigh efficiency with little or no added cost. Phosphor optimization forlaser diode modules can include highly transparent, non-scattering,ceramic phosphor plates. Decreased temperature sensitivity can bedetermined by doping levels. A reflector can be added to the backside ofa ceramic phosphor, reducing loss. The phosphor can be shaped toincrease in-coupling and reduce back reflections. Of course, there canbe additional variations, modifications, and alternatives.

For laser diodes, the phosphor or wavelength converting element can beoperated in either a transmission or reflection mode. In a transmissionmode, the laser light is shown through the wavelength convertingelement. The white light spectrum from a transmission mode device is thecombination of laser light not absorbed by the phosphor and the spectrumemitted by the wavelength converting element. In a reflection mode, thelaser light is incident on the first surface of the wavelengthconverting element. Some fraction of the laser light is reflected off ofthe first surface by a combination of specular and diffuse reflection.Some fraction of the laser light enters the phosphor and is absorbed andconverted into longer wavelength light. The white light spectrum emittedby the reflection mode device is comprised by the spectrum from thewavelength converting element, the fraction of the laser light diffuselyreflected from the first surface of the wavelength converting elementand any laser light scattered from the interior of the wavelengthconverting element.

In a specific embodiment, the laser light illuminates the wavelengthconverting element in a reflection mode. That is, the laser light isincident on and collected from the same side of the wavelengthconverting element. The element may be heat sunk to the emitter packageor actively cooled. Rough surface is for scattering and smooth surfaceis for specular reflection. In some cases, such as with a single crystalphosphor a rough surface with or without an AR coating of the wavelengthconverting element is provided to get majority of excitation light intophosphor for conversion and Lambertian emission while scattering some ofthe excitation light from the surface with a similar Lambertian as theemitted converted light. In other embodiments such as ceramic phosphorswith internal built-in scattering centers are used as the wavelengthconverting elements, a smooth surface is provided to allow all laserexcitation light into the phosphor where blue and wavelength convertedlight exits with a similar Lambertian pattern.

In a specific embodiment, the laser light illuminates the wavelengthconverting element in a transmission mode. That is, the laser light isincident on one side of the element, traverses through the phosphor, ispartially absorbed by the element and is collected from the oppositeside of the phosphor.

The wavelength converting elements, in general, can themselves containscattering elements. When laser light is absorbed by the wavelengthconverting element, the longer wavelength light that is emitted by theelement is emitted across a broad range of directions. In bothtransmission and reflection modes, the incident laser light must bescattered into a similar angular distribution in order to ensure thatthe resulting white light spectrum is substantially the same when viewedfrom all points on the collecting optical elements. Scattering elementsmay be added to the wavelength converting element in order to ensure thelaser light is sufficiently scattered. Such scattering elements mayinclude: low index inclusions such as voids, spatial variation in theoptical index of the wavelength converting element which could beprovided as an example by suspending particles of phosphor in a matrixof a different index or sintering particles of differing composition andrefractive index together, texturing of the first or second surface ofthe wavelength converting element, and the like.

In a specific embodiment, a laser or SLED driver module is provided. Forexample, the laser driver module generates a drive current, with thedrive currents being adapted to drive a laser diode to transmit one ormore signals such as digitally encoded frames of images, digital oranalog encodings of audio and video recordings or any sequences ofbinary values. In a specific embodiment, the laser driver module isconfigured to generate pulse-modulated signals at a frequency range ofabout 50 to 300 MHz, 300 MHz to 1 GHz or 1 GHz to 100 GHz. In anotherembodiment the laser driver module is configured to generate multiple,independent pulse-modulated signal at a frequency range of about 50 to300 MHz, 200 MHz to 1 GHz or 1 GHz to 100 GHz. In an embodiment, thelaser driver signal can be modulated by an analog voltage or currentsignal.

FIG. 8A is a functional block diagram for a laser-based white lightsource containing a blue pump laser and a wavelength converting elementaccording to an embodiment of the present invention. In someembodiments, the white light source is used as a “light engine” forstatic lighting, dynamic light, VLC, or smart lighting applications.Referring to FIG. 8A, a blue or violet laser device 1202 emitting aspectrum with a center point wavelength between 390 and 480 nm isprovided. The light from the blue laser device 1202 is incident on awavelength converting element 1203 which partially or fully converts theblue light into a broader spectrum of longer wavelength light such thata white light spectrum is produced. A laser driver 1201 is providedwhich powers the laser device 1202. In a preferred embodiment the laserdiode device is a gallium and nitrogen containing laser diode deviceoperating in the 395 nm to 425 nm wavelength range, 425 nm to 490 nmwavelength range, or 490 nm to 550 nm range. For example, the laserdiode is a blue laser diode with an output power of less than 1 W, orabout 1 W to about 4 W, or about 4 W to about 10 W. In some embodiments,one or more beam shaping optical elements 1204 may be provided in orderto shape or focus the white light spectrum. Optionally, the one or morebeam shaping optical elements 1204 can be one selected from slow axiscollimating lens, fast axis collimating lens, aspheric lens, ball lens,total internal reflector (TIR) optics, parabolic lens optics, refractiveoptics, or a combination of above. In other embodiments, the one or morebeam shaping optical elements 1204 can be disposed prior to the laserlight incident to the wavelength converting element 1203.

FIG. 8B is a functional block diagram for a laser-based white lightsource containing multiple blue pump lasers and a wavelength convertingelement according to another embodiment of the present invention.Referring to FIG. 8B, a laser driver 1205 is provided, which delivers adelivers a controlled amount of current at a sufficiently high voltageto operate three laser diodes 1206, 1207 and 1208. In a preferredembodiment the laser diode devices are gallium and nitrogen containinglaser diode devices operating in the 395 nm to 425 nm wavelength range,425 nm to 490 nm wavelength range, or 490 nm to 550 nm range. Forexample, the three laser diodes are blue laser diodes with an aggregatedoutput power of less than 1 W, or about 1 W to about 6 W, or about 6 Wto about 12 W, or about 12 W to 30 W. The three blue laser devices 1206,1207 and 1208 are configured to have their emitted light to be incidenton a wavelength converting element 1209 in either a transmission orreflection mode. The wavelength converting element 1209 absorbs a partor all the blue laser light and emits photons with longer wavelengths.The spectra emitted by the wavelength converting element 1209 and anyremaining laser light are collected by beam shaping optical elements1210, such as lenses or mirrors, which direct the light with a preferreddirection and beam shape. Optionally, the wavelength converting element1209 is a phosphor-based material. Optionally, more than one wavelengthconverting elements can be used. Optionally, the bean shaping opticalelements can be one or a combination of more selected the list of slowaxis collimating lens, fast axis collimating lens, aspheric lens, balllens, total internal reflector (TIR) optics, parabolic lens optics,refractive optics, and others. Optionally, the beam shaping opticalelement is implemented before the laser light hits the wavelengthconverting element.

In another embodiment, an optical fiber is used as the waveguide elementwherein on one end of the fiber the electromagnetic radiation from theone or more laser diodes is in-coupled to enter the fiber and on theother end of the fiber the electromagnetic radiation is out-coupled toexit the fiber wherein it is then incident on the phosphor member. Theoptical fiber could have a transport length ranging from 100 μm to about100 m, or to about 1 km, or greater. The optical fiber could becomprised of a single mode fiber (SMF) or a multi-mode fiber (MMF), withcore diameters ranging from about 1 μm to 10 μm, about 10 μm to 50 μm,about 50 μm to 150 μm, about 150 μm to 500 μm, about 500 μm to 1 mm, orgreater than 1 mm. The optical core material may consist of a glass suchas silica glass wherein the silica glass could be doped with variousconstituents and have a predetermined level of hydroxyl groups (OH) foran optimized propagation loss characteristic. The glass fiber materialmay also be comprised of a fluoride glass, a phosphate glass, or achalcogenide glass. In an alternative embodiment, a plastic opticalfiber is used to transport the laser pump light.

FIG. 9A is a functional block diagram for a laser-inducedfiber-delivered white light source according to an embodiment of thepresent invention. This diagram is merely an example, which should notunduly limit the scope of the claims. One of ordinary skill in the artwould recognize many variations, alternatives, and modifications. Asshown, the laser-induced fiber-delivered white light source has a laserdriver 1211 configured to provide one or more driving currents orvoltages or modulation control signals. The laser-inducedfiber-delivered white light source also includes at least one blue laserdevice 1212 configured to emit a laser light with a blue wavelength in arange from about 385 nm to about 485 nm. Optionally, the at least onelaser diode device 1212 is a LD chip configured as a chip-on-submountform having a Gallium and Nitrogen containing emitting region operatingin one wavelength selected from 395 nm to 425 nm wavelength range, 425nm to 490 nm wavelength range, and 490 nm to 550 nm range. Optionally,the at least one laser diode device 1212 includes a set of multiplelaser diode (LD) chips. Each includes an GaN-based emission stripeconfigured to be driven by independent driving current or voltage fromthe laser driver 1211 to emit a laser light. All emitted light from themultiple LD chips can be combined to one beam of electromagneticradiation. Optionally, the multiple LD chips are blue laser diodes withan aggregated output power of less than 1 W, or about 1 W to about 10 W,or about 10 W to about 30 W, or about 30 W to 100 W, or greater.Optionally, each emitted light is driven and guided separately.

In the embodiment, the laser-induced fiber-delivered white light sourceincludes a waveguide device 1214 configured to couple and deliver thelaser light from the at least one laser diode device 1212 to a remotedestination. Optionally, the waveguide device 1214 is an optical fiberfor being relatively flexibly disposed in any custom-designed lightsystem. The optical fiber includes a single mode fiber or multiple modefiber with a core diameter in a range selected from about 1 μm to 10 μm,about 10 μm to 50 μm, about 50 μm to 150 μm, about 150 μm to 500 μm,about 500 μm to 1 mm, or greater than 1 mm. Optionally, the waveguidedevice 1214 is a semiconductor waveguide pre-fabricated on asemiconductor substrate to fit a relative flexible light path in anycustom-designed light system. The waveguide device 1214 can have anarbitrary length to deliver the laser electromagnetic radiation througha waveguide transport member which terminate at a light head memberdisposed at the remote destination. Optionally, the laser light exitingthe light head is characterized by a beam diameter ranging from 1 μm to5 mm and a divergence ranging from 0 degree to 200 degrees full angle.

In the embodiment, the laser-induced fiber-delivered white light sourcealso includes a wavelength converting element 1215 disposed in the lighthead member at the remote destination. Optionally, the wavelengthconverting element 1215 is a phosphor material configured to be a singleplate or a pixelated plate disposed on a submount material completelyseparated from the laser diode device 1212. Optionally, the phosphormaterial used in the fiber-delivered laser lighting system is comprisedof a ceramic yttrium aluminum garnet (YAG) doped with Ce or a singlecrystal YAG doped with Ce or a powdered YAG comprising a bindermaterial. The phosphor material is configured to convert at leastpartially the incoming laser electromagnetic radiation of a firstwavelength (e.g., in blue spectrum) to a phosphor emission of a secondwavelength. The second wavelength is longer than the first wavelength.Optionally, the second wavelength is in yellow spectrum range.Optionally, the phosphor material has an optical conversion efficiencyof greater than 50 lumen per optical watt, greater than 100 lumen peroptical watt, greater than 200 lumen per optical watt, or greater than300 lumen per optical watt.

Optionally, the phosphor material 1215 has a surface being placed at aproximity of the end section of the optical fiber or semiconductorwaveguide in the light head member to receive the laser electromagneticradiation exited from the waveguide device 1214. Optionally, the laserelectromagnetic radiation has a primary propagation direction which isconfigured to be in an angle of incidence with respect to a direction ofthe surface of the phosphor material in a range from 20 degrees to closeto 90 degrees. Optionally, the angle of incidence of the laserelectromagnetic radiation is limited in 25 to 35 degrees. Optionally,the angle of incidence of the laser electromagnetic radiation is limitedin 35 to 40 degrees. Optionally, the end section of the waveguide device1214 in the light head member is disposed in a close proximity relativeto the surface of phosphor material so that laser electromagneticradiation can land on the surface to form an excitation spot in a rangeof 25 μm to 5 mm. Optionally, the excitation spot is limited within 50μm to 500 μm. The laser electromagnetic radiation at the excitation spotis absorbed by the phosphor material to induce a phosphor emission witha spectrum of longer wavelengths than the first wavelength of theincoming electromagnetic radiation. A combination of the phosphoremission of a second wavelength plus a partial mixture with the laserelectromagnetic radiation of the first wavelength produces a white lightemission. Optionally, the white light emission is substantiallyreflected from the surface of the phosphor material and redirected orshaped as a white light beam used for various applications. Optionally,the white light emission out of the phosphor material can be in a rangeselected from 10 to 100 lm, 100 to 500 lm, 500 to 1000 lm, 1000 to 3000lm, and greater than 3000 lm. Alternatively, the white light emissionout of the light head member as a white light source with a luminance of100 to 500 cd/mm², 500 to 1000 cd/mm², 1000 to 2000 cd/mm², 2000 to 5000cd/mm², and greater than 5000 cd/mm².

FIG. 9B is a functional block diagram for a laser-inducedfiber-delivered white light source according to another embodiment ofthe present invention. This diagram is merely an example, which shouldnot unduly limit the scope of the claims. One of ordinary skill in theart would recognize many variations, alternatives, and modifications. Asshown, the laser-induced fiber-delivered white light source includes ablue laser device 1222 driven by a laser driver 1221 to emit a laserlight with a blue emission characterized by a wavelength ranging from395 nm to 550 nm. Optionally, the laser device is a laser diode (LD)chip configured as a Chip-on-submount form with a GaN-based emittingregion operating in a first wavelength selected from 395 nm to 425 nmwavelength range, 425 nm to 490 nm wavelength range, and 490 nm to 550nm range. The laser light exits the emitting region as a beam ofelectromagnetic radiation with relatively large divergence.

Optionally, the laser-induced fiber-delivered white light sourceincludes one or more beam collimation and focus elements 1223 configuredto confine or shape the beam of electromagnetic radiation. The one ormore beam collimation and focus elements 1223 may include a collimationlens, a focus lens, a filter, a beam splitter for guiding the beam ofelectromagnetic radiation to a specific direction with reduced beamdiameter and smaller divergence. In the embodiment, the laser-inducedfiber-delivered white light source also includes a waveguide device1224. Optionally, the waveguide device 1224 is substantially similar tothe waveguide device 1214 described in earlier sections. The waveguidedevice 1224 is configured to receive the laser beam with properalignment to an output port of the laser package holding the blue laserdevice 1222 to couple the laser electromagnetic radiation into anarrowed light path in sufficiently high efficiency greater than 60% oreven greater than 80%. The waveguide device 1224 is configured todeliver the laser electromagnetic radiation to a remote destination forvarious specific applications.

In the embodiment, the laser-induced fiber-delivered white light sourcefurther includes a wavelength converting element 1225. Optionally, thewavelength converting element 1225 includes at least a phosphor materialdisposed in a remote location completely separated from the laserdevices and is able to receive the laser electromagnetic radiationexiting the waveguide device 1224. The laser electromagnetic radiationinteracts with the phosphor material within an excitation spot to inducea phosphor emission which has a second wavelength that is longer thanthe first wavelength of the laser electromagnetic radiation. A mixtureof a portion of laser electromagnetic radiation of the first wavelengthwith the phosphor emission of the second wavelength produces a whitelight emission. The white light emission is used for many illuminationand projection applications statically and dynamically. Optionally, thewhite light emission out of the phosphor material is achieved in 10 to100 lm, 100 to 500 lm, 500 to 1000 lm, 1000 to 3000 lm, and greater than3000 lm. Alternatively, the white light emission generated by the laserinduced has a luminance of 100 to 500 cd/mm², 500 to 1000 cd/mm², 1000to 2000 cd/mm², 2000 to 5000 cd/mm², and greater than 5000 cd/mm².

FIG. 9C is a functional block diagram for a multi-laser-basedfiber-delivered white light source according to yet another embodimentof the present invention. This diagram is merely an example, whichshould not unduly limit the scope of the claims. One of ordinary skillin the art would recognize many variations, alternatives, andmodifications. As shown, the multi-laser-based fiber-delivered whitelight source includes a first blue laser device 1232, a second bluelaser device 1233, and a third blue laser device 1234, commonly drivenby a laser driver 1231. Optionally, there can be more than three laserdevices driven by one or more laser drivers. Optionally, each laserdevice is configured to emit a laser light with a blue emission in onewavelength ranging from 395 nm to 550 nm. Optionally, the wavelengthrange can be limited in one selected from 395 nm to 425 nm wavelengthrange, 425 nm to 490 nm wavelength range, and 490 nm to 550 nm range.Optionally, each blue laser device, 1232, 1233, and 1234, includes alaser diode (LD) chip configured in Chip-on-submount form with a Galliumand Nitrogen containing emitting region to emit the blue laser light.Optionally, all emitted blue laser light from the multiple laser diodedevices can be combined to one laser beam by one or more beam couplingelements 1235. Optionally, the one combined laser beam of themulti-laser-based filter delivered white light source is configured toprovide a beam of electromagnetic radiation of a first wavelength inblue spectrum with an aggregated output power of less than 1 W, or about1 W to about 10 W, or about 10 W to about 30 W, or greater.

In the embodiment, the multi-laser-based fiber-delivered white lightsource includes a fiber assembly 1236 configured to align fiber core tothe combined laser beam of electromagnetic radiation so that the about60% or greater, or 80% or greater efficiency of the combined laser beamof electromagnetic radiation can be coupled into an optical fiberembedded within the fiber assembly 1236. The fiber assembly 1236 issubstantially similar the waveguide device 1214 and 1224 for deliveringthe laser electromagnetic radiation to a remote destination via aflexible or customized light path in the optical fiber with an arbitrarylength (e.g., over 100 m). At the end of the optical fiber, the laserelectromagnetic radiation of the first wavelength exits with a confinedbeam diameter and restricted divergence.

In the embodiment, the multi-laser-based fiber-delivered white lightsource includes a wavelength converting element 1237 disposed in a lighthead member at the remote destination to receive the laser beam exitingan end section of the optical fiber. In a specific embodiment, thewavelength converting element 1237 includes a phosphor plate or apixelated phosphor plate disposed in the light head member at proximityof the end section of the optical fiber so that the beam ofelectromagnetic radiation exited the optical fiber can land in an spoton an surface of the phosphor plate with a spot size limited in a rangeof about 50 μm to 5 mm. Optionally, the phosphor plate used in thefiber-delivered laser lighting system is comprised of a ceramic yttriumaluminum garnet (YAG) doped with Ce or a single crystal YAG doped withCe or a powdered YAG comprising a binder material. The phosphor platehas an optical conversion efficiency of greater than 50 lumen peroptical watt, greater than 100 lumen per optical watt, greater than 200lumen per optical watt, or greater than 300 lumen per optical watt. Thephosphor plate absorbs the blue emission lasering the beam ofelectromagnetic radiation of the first wavelength to induce a phosphoremission of a second wavelength in yellow or violet spectra range.Optionally, the phosphor emission of the second wavelength is partiallymixed with a portion of the incoming/reflecting beam of electromagneticradiation of the first wavelength to produce a white light beam.Optionally, the light head member is configured to set the relativeposition of the end section of the optical fiber on a sloped body tomake an angle of incidence of the exiting electromagnetic radiation withrespect to a direction of the surface of the phosphor plate in a rangefrom 5 degrees to 90 degrees. Optionally, the angle of incidence isnarrowed in a smaller range from 25 degrees to 35 degrees or from 35degrees to 40 degrees. Optionally, the white light emission issufficiently reflected out of the phosphor plate.

In the embodiment, the multi-laser-based fiber-delivered white lightsource optionally includes one or more beam shaping optical elements1238. In an embodiment, the one or more beam shaping optical elements1238 includes a light head member which provides a mechanical fixturefor holding the end section of the optical fiber for outputting thelaser electromagnetic radiation and supporting the phosphor plate via asubmount. Optionally, the mechanical fixture includes a sloped metalbody to support the end section of the optical fiber in an angleddirection with respect to the phosphor plate which is disposed at abottom region of the sloped metal body. Optionally, the mechanicalfixture includes a heatsink associated with the submount to support thephosphor plate for facilitating heat conduction from the hot phosphormaterial to the heatsink during a heated wavelength conversion processwhen the laser beam with high power illuminates in a small excitationspot on the surface of the phosphor plate. Optionally, the mechanicalfixture includes a reflecting semi-cone structure for facilitatingcollection of the white light emission from the surface of the phosphorplate. In another embodiment, the one or more beam shaping opticalelements 1238 includes additional secondary optics elements for handlingthe white light emission generated by the multi-laser-basedfiber-delivered white light source. These secondary optics elementsinclude static free-space optical elements, fiber-based opticalelements, semiconductor-based optical elements, or one or more opticalelements that are dynamically controlled for providing smart lightinginformation or information projection.

FIG. 10A is a simplified diagram illustrating multiple discrete lasersconfigured with an optical combiner according to embodiments of thepresent invention. As shown, the diagram includes a package or enclosurefor multiple laser diode light emitting devices. In a preferredembodiment the laser diode light-emitting devices are gallium andnitrogen containing laser diode devices operating in the 395 nm to 425nm wavelength range, 425 nm to 490 nm wavelength range, or 490 nm to 550nm range. For example, the multiple laser diode emitters are blue laserdiodes with an aggregated output power of less than 1 W, or about 1 W toabout 10 W, or about 10 W to about 30 W, or about 30 W to 100 W, orgreater. Each of the devices is configured on a single ceramic ormultiple chips on a ceramic, which are disposed on common heat sink. Asshown, the package includes all free optics coupling, collimators,mirrors, spatially or polarization multiplexed for free space output orrefocused in a fiber or other waveguide medium. As an example, thepackage has a low profile and may include a flat pack ceramic multilayeror single layer. The layer may include a copper, a copper tungsten basesuch as butterfly package or covered CT mount, Q-mount, or others. In aspecific embodiment, the laser devices are soldered on CTE matchedmaterial with low thermal resistance (e.g., AlN, diamond, diamondcompound) and forms a sub-assembled chip on ceramics. The sub-assembledchip is then assembled together on a second material with low thermalresistance such as copper including, for example, active cooling (i.e.,simple water channels or micro channels), or forming directly the baseof the package equipped with all connections such as pins. The flatpackis equipped with an optical interface such as window, free space optics,connector or fiber to guide the light generated and a coverenvironmentally protective.

FIG. 10B is an example of enclosed free space laser module. A case 1400is used for assembling a free-space mirror-based laser combiner. Thelaser module includes two electrical supply pins 1410 for providingdriving voltages for the laser diodes 1430. In a preferred embodimentthe laser diode devices are gallium and nitrogen containing laser diodedevices operating in the 395 nm to 425 nm wavelength range, 425 nm to490 nm wavelength range, or 490 nm to 550 nm range. For example, themultiple laser diode emitters are blue laser diodes with an aggregatedoutput power of less than 1 W, or about 1 W to about 10 W, or about 10 Wto about 30 W, or greater. The case 1400 includes a hole for a fiber1460 to couple with the light guide output combined from all laserdiodes 1430 through the series of mirrors 1450. An access lid 1420 isdesigned for easy access of free-space optical elements 1440 in theassembly. A compact plug-and-play design provides a lot of flexibilitiesand ease of use.

FIG. 10C is a schematic of an enclosed free space multi-chip lasermodule with an extended delivery fiber plus phosphor converter accordingto a specific embodiment of the present invention. As shown, theenclosed free space multi-chip laser module is substantially similar tothe one shown in FIG. 10A with two electrical supply pins 1410 toproduce a laser light beam in violet or blue light spectrum. Themultiple laser chips 1430 in the package equipped with free-space opticsunits 1455 provide substantially high intensity for the light sourcethat is desired for many new applications. Additionally, an extendedoptical fiber 1465 with one end is coupled with the light guide outputfor further guiding the laser light beam to a desired distance forcertain applications up to 100 m or greater. Optionally, the opticalfiber can be also replaced by multiple waveguides built in a planarstructure for adapting silicon photonics integration. At the other endof the optical fiber, a phosphor-based wavelength converter 1470 may bedisposed to receive the laser light, where the violet or blue colorlaser light is converted to white color light 1475 and emitted outthrough an aperture or collimation device. As a result, a white lightsource with small size, remote pump, and flexible setup is provided.

FIG. 11 is a perspective view of a fiber-delivered white light sourceincluding a general laser package and a light head member including awavelength conversion phosphor member wherein the laser package and thelight head member are linked to each other via a fiber assemblyaccording to an embodiment of the present invention. This diagram ismerely an example, which should not unduly limit the scope of theclaims. One of ordinary skill in the art would recognize manyvariations, alternatives, and modifications. As shown, a fiber-deliveredwhite light source 1500 includes at least a general laser package 1510for laser and a light head member 1520 connected by a fiber assembly1530. The general laser package 1510 is a metal case for enclosing alaser module therein having an electrical connector 1512 disposedthrough a cover member 1511 for providing electrical supply to thedevices in the case. The bottom side (not visible) is for mounting to aheat conductive base for distributing heat out of the heat-generatinglaser device. The light head member 1520 is metal case with a slopedshape and a glass window 1522 covering the slopped facet, enclosing aphosphor material inside (not shown) for receiving laser light deliveredby the fiber assembly 1530 and converting the laser emission to a whitelight emission. The bottom side (not visible) od the light head member1530 is made by metal or other thermal conductive material forefficiently distributing heat generated by the phosphor materialtherein. The fiber assembly 1530 shown in FIG. 11 is visible with asemi-flexible metal armor used to protect the optical fiber insidethroughout an extended length from a first end coupled to the generallaser package 1510 and a second end coupled with the light head member1520 at a remote destination. The extended length can be over 100 m.

FIG. 12 is a top view of the general laser package of FIG. 11 accordingto the embodiment of the present invention. This diagram is merely anexample, which should not unduly limit the scope of the claims. One ofordinary skill in the art would recognize many variations, alternatives,and modifications. As shown, the electrical connector 1512 with multiplepins are disposed via an electrical feedthrough at the top cover member1511 of the general laser package 1510. The opposite side of the generallaser package is a bottom member used for mounting the general laserpackage 1510 in applications. The bottom member is preferred to be madeby metal or metal alloy material, for example, AlN, AlO, BeO, Diamond,CuW, Cu, or Silver, or other high thermal conductive materials formounting on a heatsink to quickly distributing heat generated by laserdevices inside the package 1510.

FIG. 13 is a top view of interior elements of the general laser packageof FIG. 12 including a blue-laser module mounted on an electroniccircuit board according to the embodiment of the present invention. Thisdiagram is merely an example, which should not unduly limit the scope ofthe claims. One of ordinary skill in the art would recognize manyvariations, alternatives, and modifications. The general laser package1510B of FIG. 13 is substantially the same general laser package 1510 ofFIG. 12 with the top cover member 1511 being removed. As shown, thegeneral laser package 1510B encloses a board member 1515 on which theelectrical connector 1512 and multiple resistors and capacitors or otherelectronic components are mounted. Primarily, a blue-laser module 1580is disposed in a center region with multiple electrical pins pluggedinto the board member 1515. A fixing member 1516 is placed on top of theblue-laser module 1580 for securing the mounting of the blue-lasermodule 1580. An output port 1587 is coupled to the blue-laser module1580 from one side thereof and also coupled to the fiber assembly (withthe metal armor of the optical fiber being partially visible). In theembodiment, the blue-laser module 1580 is configured to generatehigh-power laser light for the fiber-delivered white light source 1500(FIG. 11 ). For example, the blue laser module contains one or morelaser diode chips with gallium and nitrogen containing emitting regionconfigured to generate a laser electromagnetic radiation of a firstwavelength in blue spectrum range with a power less than 1 W, or about 1W to about 3 W, or about 3 W to about 10 W, or about 10 W to 100 W, orgreater than 100 W.

FIG. 14 is a top view of the blue-laser module with opened lid accordingto an embodiment of the present invention. This diagram is merely anexample, which should not unduly limit the scope of the claims. One ofordinary skill in the art would recognize many variations, alternatives,and modifications. As shown, the blue-laser module 1800 is configured asa metal case 1801 (with lid opened) enclosing a support member 1802 forsupporting multiple components: at least one laser diode device 1810, acollimating lens 1820, a thermistor 1830, a beam splitter 1840, a firstphotodetector 1850, a focus lens 1860, an output port 1870, and a secondphotodetector 1880. Optionally, the laser diode device 1810 is aconfigured to be a chip-on-submount (CoS) device having a Gallium andNitrogen (GaN) containing active region which is driven to generate alaser light with primary emission spectrum in blue region ranging from415 nm to 485 nm. Optionally, the laser diode device 1810 is mounted ona ceramic base member on the support member 1802. In an embodiment, theceramic base member is a High Temperature Co-fired Ceramic (HTCC)submount structure configured to embed electrical conductors therein forconnecting the laser diode with its driver, and to provide sufficientlyefficient thermal conduction for the laser diode during operation.

In an embodiment, the laser light generated by the laser diode device1810 exits with a large spread into a collimating lens 1820 to form alaser beam with a reduced spot size and a narrowed spread range.Optionally, the collimating lens 1820 is disposed in front of an exitfacet of the GaN active region of the CoS chip 1810 and fixed by a weldclip. A thermistor 1830 is disposed near the laser diode device 1810 asa temperature sensor for monitoring temperature during operation.Optionally, an electrostatic discharge (ESD) Zener diode is included toprotect the laser diode device from static electrical shock.

In the embodiment, the beam splitter 1840 is disposed in the path of thecollimated laser beam. Optionally, the beam splitter 1840 is a filter.Optionally, beam splitter 1840 is an optical crystal with a front facetand a back facet. The front facet of the beam splitter faces theincoming laser beam and is coated with an anti-reflection thin-film forenhancing transmission. Optionally, a small amount of laser light stillis reflected. The first photodetector 1850 is placed (to the left) todetect the reflected light. Optionally, the photodiode 1850 is the firstphotodetector characterized to detect primarily blue emission for safetysensing of the laser diode device 1810. The back facet of the beamsplitter allows that a primary first portion of the laser beam is exitedin a first direction while a minor second portion with the blue emissionbeing substantially filtered is split to a second direction deviatedfrom the first direction. The second photodetector 1880 is placed (tothe right) to detect yellow spectrum for monitoring the second portionof the laser beam with the blue emission being substantially filtered.Optionally, an extra filter is placed in front of the secondphotodetector 1880.

In the embodiment, the primary first portion of the laser beam exitedfrom the beam splitter 1840 is led to a focus lens 1860 disposed insidethe metal case 1801. Optionally, the focus lens 1860 is configured toconfine the laser beam to much smaller size that can be coupled into anoptical fiber. Optionally, the Optionally, the coupling efficiency ofthe laser beam into the optical fiber is achieved and maintained greaterthan 80%. Optionally, the focus lens 1860 is mounted to the output port1870 from inside of the metal case 1801. The optical port 1870 is360-degree laser weld in a through hole at one side wall of the metalcase 1801. Referring to FIG. 13 , a first end of the fiber assembly 1530is configured to couple with the output port which is denoted as 1587.

In the embodiment, the blue-laser module 1800 also includes multiplepins 1890 that are disposed at two opposite sides of the metal case1801. One end of each pin is connected to the electrical connectorembedded in the ceramic base member. Another end of each pin is bendeddown to plug into the board member 1515 (see FIG. 13 ) so that theblue-laser module 1800 can receive electrical driver/control signals.

FIG. 15 is a perspective view of the blue-laser module according to theembodiment of the present invention. Referring to FIG. 15 , it shows asubstantially same blue-laser module of FIG. 14 for better illustratingthe structural layout of each components mentioned herein.

FIG. 16 is (A) a top view of a general laser package, (B) a top view ofinterior elements of the general laser package including a blue-lasermodule, and (C) a top view of the blue-laser module according to anotherembodiment of the present invention. These diagrams are merely anexample, which should not unduly limit the scope of the claims. One ofordinary skill in the art would recognize many variations, alternatives,and modifications. In the embodiment shown in the FIG. 16 , in part A,the top cover member 2011 of a general laser package 2010 is seen withan electrical connector 2012 disposed therein. An output port 2017 isconfigured to couple with a fiber assembly. In part B, the general laserpackage 2010B is shown without the top cover member 2011. The electricalconnector 2012 is seen mounted on a board member 2015. A blue-lasermodule 2080 is partially visible is also mounted on the board member2015 with several pins visibly located at two opposite sides while alarge piece of fixing clip 2016 is placed on top of the blue-lasermodule 2080. A focus lens 2087 is disposed outside the blue-laser module2080 and coupled with the fiber assembly at the output port 2017 (seepart A). In part C, the blue-laser module 2080 is shown as a metal case2081 with its lid opened. The blue-laser module 2080 in the embodimentincludes at least a laser diode device 2082 disposed on a support member2087 to generate a laser light, a collimating lens 2088 disposed andaligned to one facet of an emitting stripe of the laser diode device2082 in an optical path of the laser light, and a beam splitter 2084disposed down-stream of the optical path of the laser light. Optionally,multiple laser diode devices configured respectively as Chip-on-SubmountLD chips can be laid in the metal case 2081 of the blue-laser module forachieving higher laser power. Optionally, multiple laser beams frommultiple LD chips can be combined to reach unified power of 6 W, or 12W, or 15 W for obtaining a brighter white light.

In the embodiment, the laser diode device 2082 includes an active regionmade by Gallium Nitride having the emitting stripe configured to emitlight from one end facet. Optionally, the emitted light is substantiallya blue emission with a wavelength in a range from 415 nm to 485 nm. Thesupport member 2087 optionally is a High Temperature Co-fired Ceramic(HTCC) submount structure configured to embed electrical conductingwires therein. This type of ceramic support member provides high thermalconductivity for efficiently dissipating heat generated by the laserdiode 2082 to a heatsink that is made to contact with the support member2087. The ceramic support member 2087 also can allow optimizedconduction wire layout so that ESD can be prevented and thermalmanagement of the whole module can be improved. Referring to part C ofFIG. 16 , at least two electrical pins 2089 are configured to connectwith the conducting wires in the HTTC ceramic submount structure forproviding external drive signals for the laser diode 2082. Optionally,the blue-laser module 2080 includes a temperature sensor 2083 that canbe disposed within the metal case on the support member and relative faraway from the location of the laser diode 2082.

In the embodiment, the light generated by the laser diode device 2082 isled into the collimating lens 2088 so that the light can be confinedwith a smaller spread range to form a laser beam along a first direction(x). Optionally, the beam splitter 2084 is disposed down stream of anoptical path along the first direction x, and is configured to split thelaser beam to at least a first portion primarily in the first directionx and a second portion redirected to a second direction y. The firstportion of the laser beam remains primarily a blue emission. The secondportion may be filtered to eliminate the blue spectrum while retainingminor yellow spectrum. In the embodiment, the blue-laser module 2080further includes a photo diode 2085 disposed in the path of the seconddirection y inside the metal case 2081 to detect the yellow spectrum.

FIG. 17 is a partial cross-sectional view of an end section of a fiberassembly according to an embodiment of the present invention. Thisdiagram is merely an example, which should not unduly limit the scope ofthe claims. One of ordinary skill in the art would recognize manyvariations, alternatives, and modifications. As shown, in an embodiment,the end section of the fiber assembly 1700 is supposed to be coupledwith the laser module 1800 (see FIG. 15 ). An optical fiber 1701 isembedded in the fiber assembly 1700. Optionally, the optical fiber 1701is comprised of a single mode fiber (SMF) or a multi-mode fiber (MMF),with core diameters ranging from about 1 um to 10 um, about 10 um to 50um, about 50 um to 150 um, about 150 um to 500 um, about 500 um to 1 mm,or greater than 1 mm. The optical core material may consist of a glasssuch as silica glass wherein the silica glass could be doped withvarious constituents and have a predetermined level of hydroxyl groups(OH) for an optimized propagation loss characteristic. The glass fibermaterial may also be comprised of a fluoride glass, a phosphate glass,or a chalcogenide glass. In an alternative embodiment, a plastic opticalfiber is used to transport the laser pump light. Optionally, most partof the optical fiber in a middle section of the fiber assembly 1700 isprotected by a fiber jacket. FIG. 17 shows that an end section of thefiber assembly in a ferrule 1702 is terminated in a fiber terminationadaptor 1710. Optionally, the ferrule 1702 can be made by glass, orceramic material, or metal material. Referring to FIG. 15 and FIG. 17 ,the fiber termination adaptor 1710 is coupled with an output port bylaser welding. In a specific embodiment, the fiber termination adaptor1710 includes a precision circular rim made for laser welded at itsperimeter with an inner diameter of a hole in a side wall of the lasermodule sub-package 1800 (see FIG. 15 ) for hermetical sealing. The fibertermination adaptor 1710 further has its end face 1720 being laserwelded with a lens which essentially the focus lens 1870 (see FIG. 15 )for hermetic sealing. Optionally, the focus lens 1730 (FIG. 17 ) is alsohermetically sealed around its perimeter in the lens structure 1860(FIG. 15 ). Optionally, during the fiber coupling process, an activealignment process is performed to simultaneously align a focus lens 1730(or 1860 in FIG. 15 ) to the fiber core 1701 such that the maximumamount of radiated power emitting from the laser diode through the focuslens 1730 is focused into the fiber 1701. Both the focus lens 1730 andfiber 1701 must be manipulated in the X, Y, Z linear direction withinmicron precision. In addition, the angular rotation of each axis mustalso be controlled during the alignment procedure. At the same time, thefiber assembly 1700 involving the fiber core, ferrule, fiber terminationadaptor, requires a hermetically sealed assembly in addition to the goodalignment between fiber and focus lens such that a coupling efficiencyis kept greater than 60% or even greater than 80%.

FIG. 18 is a partial cross-sectional view of an end section of a fiberassembly according to another embodiment of the present invention. Thisdiagram is merely an example, which should not unduly limit the scope ofthe claims. One of ordinary skill in the art would recognize manyvariations, alternatives, and modifications. As shown, in an alternativeembodiment, a fiber assembly 1900 includes an end section having aferrule 1902 enclosing the optical fiber 1901 therein except a smallsection of fiber core. On rest part (in the middle section) of the fiberassembly 1900, the optical fiber 1901 is protected by a fiber jacket.The ferrule 1902 is capped by a fiber termination adaptor 1910. In thisembodiment, the fiber termination adaptor design is made to include alens 1930 at its very end, allowing passive alignment of severalrelative positions between the lens 1930 and fiber core 1901. In theembodiment, the lens 1930 can be disposed at a concentricity positionvia mechanical references, eliminating the X, Y motion requirement ofthe lens. A precision spacer (not shown) allows the Z-axis position tobe passively obtained to achieve desired alignment with sufficientlyhigh coupling efficiency. The fiber termination adaptor 1910 has aprecision rim for laser welded at its perimeter with the inner diameterof a hole in the side wall of the laser module 2080 (see FIG. 16 ).Optionally, the fiber assembly 1900 can be actively aligned, during itswelding process with the laser module 2080, to the radiated poweremitting from the laser diode with relaxed requirements. For example,the precision requirement can be relaxed to tens of microns instead oflimiting to micron precision.

FIG. 19 is a perspective view of the light head member of FIG. 11according to an embodiment of the present invention. This diagram ismerely an example, which should not unduly limit the scope of theclaims. One of ordinary skill in the art would recognize manyvariations, alternatives, and modifications. As shown, a perspectiveview of the light head member 2300 includes a semi-open metal case 2301with a slopped body 2310. A second end of the fiber assembly 1530 isconfigured to have the optical fiber 1535 to pass through an input port2320 and be bended in parallel with the slopped body 2310. The sloppedbody 2310 further includes a reflecting semi-cone 2330 formed at a lowerpart where the optical fiber 1535 ended with a fiber head 1538 forguiding the laser beam into a surface of phosphor material 2350 with anangle. Optionally, the reflecting semi-cone 2330 is coated with a highlyreflective material for white light.

In the embodiment, the phosphor material 2350 is disposed at a bottomregion of the reflecting semi-cone 2330. The angle of the laser beamguided by the fiber head 1538 is relative to the surface of the phosphormaterial 2350. Optionally, the angle of the laser beam hitting thesurface of phosphor can be set in a range from 30 degrees to 35 degrees.As the laser beam with blue emission is directed from the fiber head1538 into a small spot 2355 in the surface of the phosphor material2350, it excited the phosphor material 2350 to convert the received blueemission to a phosphor-excited emission with a longer wavelength (forexample, a violet emission). Optionally, the spot size on the surface ofthe phosphor material 2350 is confined within 500 μm and even down to 50μm. A mixing of the phosphor-excited emission with the blue emission ofthe laser beam forms a white light beam 2340 exiting (or substantiallyreflected by) upwards from the reflecting semi-cone 2330. Optionally,the phosphor material is mounted on a heatsink to conduct heat quicklyaway from the excited phosphor material when it is illuminated by ahigh-power laser emission. Optionally, a glass window material is placedoverlying the slopped body and allow the white light beam to passthrough to serve as a white light source. Optionally, the white lightsource is configured to produce substantially pure white light withstrong luminance of flux in 250, 500, 1000, 3000, and 10,000 cd/mm².

In an embodiment, the fiber assembly 1530 integrated in thefiber-delivered laser induced white light system 1500 (see FIG. 11 ) canbe made to be detachable so that applications of the system can be moreflexible for maintenance. For example, a portion of failed parts can beeasily replaced without disrupting the whole system. Optionally,referring to FIG. 11 , the system 1500 can be provided with a detachablefiber termination adaptor (FTA) at an input port of the fiber assembly1530 coupled with the main laser package 1510. Optionally, any place inthe middle section of the fiber assembly 1530 can be selected forforming a fiber coupling joint using either mechanical fiber-to-fibercoupling mechanism or optical recoupling mechanism. FIG. 20 shows anexemplary diagram of a fiber coupling joint made by mechanical buttcoupler according to an embodiment of the present invention. As shown,each of two attachable sections of the fiber assembly 1530 arerespectively terminated with two connectors 2100 and 2200. Optionally,the connector 2100 is characterized by a total length L1 including aconnector length L2 plus a boot 2130 and a connector size H. Eachconnector (2100) is coupled with the optical fiber (not explicitlyshown) via a ferrule structure 2110 with one end being inserted into theconnector 2100 with alignment to minimize fiber core offset, witheye-damaging prevention, and with dust protection. Another end of theferrule is coupled first with a sleeve member 2120 before inserted intoa bend-protection boot 2130. Two connectors 2100 and 2200 are matedtogether when they are respectively inserted into two entries of amating adaptor 2010. The location of the coupling joint can be easilyimplemented into existing product.

In another embodiment, the fiber connector sets for forming the couplingjoint can be made with lenses for optical recoupling. In this case,free-space optical elements are used for ensuring good optical couplingwith substantially free of mechanical misalignment. Optionally, theoptical-recoupling set includes window(s) for conveniently cleaning.

In yet another embodiment, referring to FIG. 11 , the system 1500 can beprovided with a detachable fiber termination adaptor (FTA) at an outputport of the fiber assembly 1530 coupled with the light head member 1520.This option is substantially achieved like the FTA at the input port.

FIG. 21 shows an application of a fiber-delivered white light source forstreet lighting according to an embodiment of the present invention.This diagram is merely an example, which should not unduly limit thescope of the claims. One of ordinary skill in the art would recognizemany variations, alternatives, and modifications. As shown, thefiber-delivered white light source for street lighting includes a laserdiode bank 2800 (containing one or more gallium and nitrogen containinglaser diode chips) remotely disposed in a utility box or buriedunderground. A laser beam, substantially in blue emission in anembodiment, is delivered via an optical fiber 2806 from a bottom of astreet light pole 2805 to its top where a phosphor member 2810 is setup. In the embodiment, the phosphor member 2810 is configured to receivethe incident laser beam delivered by the optical fiber and generate awhite light beam. Optionally, the white light beam is shaped by one ormore optic elements to become wide angled beams 2815. Provided a certainheight of the street light pole 2805, the wide-angled beams 2815resulted a spread illumination region 2825 in an elongated shape alongthe street 2820. The wide spread angle of the illuminated region of suchstreet light with 100× higher luminance allows 3-5× reduction in numbersof street poles for the whole street light system. Additionally, sincethe laser diode bank is remotely disposed on or under the ground, nolift would be needed to change the bulb. This would make replacement ormaintenance cost of the light system much lower. It would also make thestreet light pole less expensive since it would not need to support theheavyweight of all the electronics and lights.

In an alternative embodiment, similar fiber-delivered white light sourcecan be developed for bridge lighting wherein the laser diode bank 2800can be disposed at two ends of the bridge on shoreline for easy accesswhile each of all lighting elements disposed on bridge can be configuredwith a light head member containing a phosphor member 2810 to receivethe lase electromagnetic radiation delivered by a waveguide transportelement such as the optical fiber 2806 from the laser diode bank 2800.Multiple fibers can be used to respectively deliver laser from the laserdiode bank 2800 to multiple different light head members. The laserdelivered by the optical fiber reaches a surface of a phosphor member ineach light head member to generate a phosphor emission for producing awhite light emission for illumination. Optionally, optics design allowsthe spread illumination region 2825 corresponding to each phosphormember 2810 to be respectively configured based on the bridge dimensionand curvature to achieve best illumination or decoration effects withthe most economic arrangement of positions, angles, heights of the lighthead member containing the phosphor member 2810.

In yet another embodiment, similar white light sources can be developedfor application of tunnel lighting, down-hole lighting, stadiumlighting, and many other special lighting applications that can takeadvantages of remotely delivering ultra strong visible lighting via thefiber-delivered white light source.

In some embodiments the fiber delivered white light source could be usedfor data transmission from the light source to devices configured toreceive the signal. For example, the laser based light source could beused for Li-Fi and visible light communication (VLC) applications totransmit at high data rates of greater than 1 Gb/s, greater than 5 Gb/s,greater than 10 Gb/s. greater than 50 Gb/s, or greater than 100 Gb/s.Such high data rates enable by used of the visible light spectrum withlaser diodes could enable new capability for applications such as theinternet of things (IOT), smart lighting, vehicle to vehiclecommunication, mobile machine communication, street lighting to vehiclecommunication, and many more. Additionally, the fiber delivered whitelight sources could be applied to LIDAR applications.

While the above is a full description of the specific embodiments,various modifications, alternative constructions and equivalents may beused. As an example, the packaged device can include any combination ofelements described above, as well as outside of the presentspecification. Although the embodiments above have been described interms of a laser diode, the methods and device structures can also beapplied to other stimulated light emitting devices. Therefore, the abovedescription and illustrations should not be taken as limiting the scopeof the present invention which is defined by the appended claims.

What is claimed is:
 1. An apparatus for remotely delivering white light,the apparatus comprising: at least one laser diode device; a packagemember with electrical feedthroughs configured to couple power from adriver to the at least one laser diode device; the package membercomprising a support member, the at least one laser diode deviceconfigured to the support member and driven by the driver to emit a beamof laser electromagnetic radiation characterized by a first wavelengthranging from 395 nm to 490 nm; a waveguide assembly having a first endsection coupled to the package member to receive the laserelectromagnetic radiation and a waveguide transport member to deliverthe laser electromagnetic radiation through a length to exit a secondend section with a propagation direction, a beam diameter, and adivergence; a phosphor member disposed in a member and configured with asurface to receive the laser electromagnetic radiation exited from thesecond end section; the phosphor member providing a wavelengthconversion of at least a fraction of the laser electromagnetic radiationof the first wavelength to a phosphor emission of a second wavelength,wherein the second wavelength is longer than the first wavelength, andthe phosphor member is configured with a mechanical fixture provided inthe member to support the phosphor member and the second end section ofthe waveguide assembly with an angle of incidence in a range from 5degrees to 90 degrees between the primary propagation direction of thelaser electromagnetic radiation and a direction parallel to the surfaceof the phosphor member and to form an excitation spot, having adimension of 25 μm to 5 mm, of the incident laser electromagneticradiation on the surface of the phosphor member, thereby generating asubstantially white light emission characterized by a mixture of thelaser electromagnetic radiation of the first wavelength and the phosphoremission of the second wavelength from the excitation spot.
 2. Theapparatus of claim 1, wherein the at least one laser diode devicecomprises multiple LD chips respectively configured as chip-on-submountforms coupled with one or more optical coupling elements to obtain acombined beam of the laser electromagnetic radiation with an aggregatedoutput power of less than 1 W, or about 1 W to about 6 W, or about 6 Wto about 12 W, or about 12 W to 30 W, or greater than 30 W.
 3. Theapparatus of claim 1, wherein the waveguide transport member comprisesan optical fiber, including a single mode fiber (SMF) or a multi-modefiber (MMF), with core diameters ranging from about 1 μm to 10 μm, about10 μm to 50 μm, about 50 μm to 150 μm, about 150 μm to 500 μm, about 500μm to 1 mm, or greater than 1 mm.
 4. The apparatus of claim 3, whereinthe optical fiber comprises a detachable joint, the detachable jointbeing configured with a pair of mechanical fiber connectors orfree-space optical couplers.
 5. The apparatus of claim 1, wherein themechanical fixture comprises a sloped body to at least support thesecond end section of the waveguide assembly to make the angle ofincidence between the primary propagation direction of the laserelectromagnetic radiation and the direction parallel the surface of thephosphor member to be one from 20 degrees to 50 degrees, or one from 30degrees to 40 degrees.
 6. The apparatus of claim 1, wherein theexcitation spot of the incident laser electromagnetic radiation exitingthe second section of the waveguide assembly is formed on the surface ofthe phosphor member in a range from 50 μm to 500 μm.
 7. The apparatus ofclaim 1, wherein the at least one laser diode device comprises achip-on-submount laser diode (LD) chip held in a sub-package, the LDchip having a gallium and nitrogen containing emitting region operatingin one wavelength selected from 395 nm to 425 nm wavelength range and425 nm to 490 nm wavelength range.
 8. The apparatus of claim 7, whereinthe sub-package further comprises a collimation lens supported on asupport member for collimating the beam of laser electromagneticradiation.
 9. The apparatus of claim 8, wherein the sub-package furthercomprises a focus lens coupled to an output port from inside forcoupling the beam of laser electromagnetic radiation with about 60% orgreater efficiency.
 10. The apparatus of claim 9, wherein thesub-package further comprises a beam splitter disposed on the supportmember with an angle of about 45 degrees relative to a beam directionbetween the collimation lens and the focus lens, the beam splittercomprises a first surface reflecting a small portion of the laser beamand passing a major portion of the laser beam, and a second surface forsplitting the major portion of the laser beam to a first portion guidedto a first direction toward the focus lens and a second portion beingdirected to a second direction deviated from the first direction. 11.The apparatus of claim 10, wherein the sub-package further comprises atleast a photodiode to detect yellow spectrum for monitoring the secondportion of the laser beam with a blue emission being substantiallyfiltered, or wherein the sub-package further comprises both a firstphotodiode characterized to detect the blue emission of the reflectedsmall portion of the laser beam for sensing laser safety and a secondphotodiode characterized to detect the yellow spectrum, wherein the atleast one laser diode device is configured to be shut off if an unsafestate is detected.
 12. The apparatus of claim 7, wherein the packagemember further comprises an electronic board having a connector coupledwith the electrical feedthrough and connected to multiple sockets forplugging the sub-package for providing power and control signals fromthe driver to the at least one laser diode device therein.
 13. Theapparatus of claim 1, wherein the phosphor member comprises a ceramicyttrium aluminum garnet (YAG) doped with Ce or a single crystal YAGdoped with Ce or a powdered YAG comprising a binder material; whereinthe phosphor member has an optical conversion efficiency of greater than50 lumen per optical watt, greater than 100 lumen per optical watt,greater than 200 lumen per optical watt, or greater than 300 lumen peroptical watt.
 14. The apparatus of claim 1, wherein the white lightemission outputted from the member comprising a light head membercomprises a luminance of 100 to 500 cd/mm², 500 to 1000 cd/mm², 1000 to2000 cd/mm², 2000 to 5000 cd/mm², and greater than 5000 cd/mm².
 15. Anapparatus for remotely delivering white light, the apparatus comprising:at least one laser diode device; a package member with electricalfeedthroughs configured to couple power from a driver to the at leastone laser diode device; the package member comprising a support member,the at least one laser diode device configured to the support member anddriven by the driver to emit a beam of laser electromagnetic radiationcharacterized by a first wavelength ranging from 395 nm to 490 nm; awaveguide assembly having a first end section coupled to the packagemember to receive the laser electromagnetic radiation and a waveguidetransport member to deliver the laser electromagnetic radiation througha length to exit a second end section with a propagation direction, abeam diameter, and a divergence; a phosphor member disposed in a headmember and configured with a surface to receive the laserelectromagnetic radiation exited from the second end section; thephosphor member providing a wavelength conversion of at least a fractionof the laser electromagnetic radiation of the first wavelength to aphosphor emission of a second wavelength, wherein the second wavelengthis longer than the first wavelength, and the phosphor member isconfigured with a mechanical fixture provided in the head member tosupport the phosphor member and the second end section of the waveguideassembly with an angle of incidence in a range from 5 degrees to 90degrees between the primary propagation direction of the laserelectromagnetic radiation and a direction parallel to the surface of thephosphor member and to form an excitation spot, having a dimension of 25μm to 5 mm, of the incident laser electromagnetic radiation on thesurface of the phosphor member, thereby generating a substantially whitelight emission characterized by a mixture of the laser electromagneticradiation of the first wavelength and the phosphor emission of thesecond wavelength from the excitation spot.
 16. The apparatus of claim15, wherein the mechanical fixture comprises a sloped body to at leastsupport the second end section of the waveguide assembly to make theangle of incidence between the primary propagation direction of thelaser electromagnetic radiation and the direction parallel the surfaceof the phosphor member to be one from 20 degrees to 50 degrees, or onefrom 30 degrees to 40 degrees.
 17. The apparatus of claim 15, whereinthe at least one laser diode device comprises a chip-on-submount laserdiode (LD) chip held in a sub-package, the LD chip having a gallium andnitrogen containing emitting region operating in one wavelength selectedfrom 395 nm to 425 nm wavelength range and 425 nm to 490 nm wavelengthrange.
 18. The apparatus of claim 17, wherein the sub-package furthercomprises a collimation lens supported on a support member forcollimating the beam of laser electromagnetic radiation; or wherein thesub-package further comprises a focus lens coupled to an output portfrom inside for coupling the beam of laser electromagnetic radiationwith about 60% or greater efficiency.
 19. The apparatus of claim 17,wherein the sub-package further comprises a beam splitter disposed onthe support member with an angle of about 45 degrees relative to a beamdirection between a collimation lens and a focus lens, the beam splittercomprises a first surface reflecting a small portion of the laser beamand passing a major portion of the laser beam, and a second surface forsplitting the major portion of the laser beam to a first portion guidedto a first direction toward the focus lens and a second portion beingdirected to a second direction deviated from the first direction. 20.The apparatus of claim 19, wherein the sub-package further comprises atleast a photodiode to detect yellow spectrum for monitoring the secondportion of the laser beam with a blue emission being substantiallyfiltered, or wherein the sub-package further comprises both a firstphotodiode characterized to detect the blue emission of the reflectedsmall portion of the laser beam for sensing laser safety and a secondphotodiode characterized to detect the yellow spectrum, wherein the atleast one laser diode device is configured to be shut off if an unsafestate is detected.